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 $187.26   3.738%   $194.2598   $194.26   $194.25   $194.30  
  Purchase #2 $104.72   8.532%   $113.6547   $113.65   $113.65   $113.70  
  Purchase #3 $181.25   12.349%   $203.6326   $203.63   $203.65   $203.60  
  Purchase #4 $208.65   4.165%   $217.3403   $217.34   $217.35   $217.30  
  Purchase #5 $196.95   6.201%   $209.1629   $209.16   $209.15   $209.20  
  Purchase #6 $112.77   10.791%   $124.939   $124.94   $124.95   $124.90  
  Purchase #7 $190.93   3.818%   $198.2197   $198.22   $198.20   $198.20  
  7 purchase totals = $1,182.53       $1,261.2090   $1,261.20   $1,261.20   $1,261.20