Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $182.59   12.433%   $205.2914   $205.29   $205.30   $205.30  
  Purchase #2 $197.52   3.372%   $204.1804   $204.18   $204.20   $204.20  
  Purchase #3 $192.34   13.551%   $218.404   $218.40   $218.40   $218.40  
  Purchase #4 $104.87   12.708%   $118.1969   $118.20   $118.20   $118.20  
  Purchase #5 $182.84   4.309%   $190.7186   $190.72   $190.70   $190.70  
  Purchase #6 $130.39   7.622%   $140.3283   $140.33   $140.35   $140.30  
  Purchase #7 $133.88   11.460%   $149.2226   $149.22   $149.20   $149.20  
  7 purchase totals = $1,124.43       $1,226.3422   $1,226.34   $1,226.35   $1,226.30