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 $206.47   5.679%   $218.1954   $218.20   $218.20   $218.20  
  Purchase #2 $192.99   5.741%   $204.0696   $204.07   $204.05   $204.10  
  Purchase #3 $103.69   6.515%   $110.4454   $110.45   $110.45   $110.40  
  Purchase #4 $78.67   6.109%   $83.476   $83.48   $83.50   $83.50  
  Purchase #5 $104.56   12.153%   $117.2672   $117.27   $117.25   $117.30  
  Purchase #6 $235.36   5.647%   $248.6508   $248.65   $248.65   $248.70  
  Purchase #7 $202.49   5.678%   $213.9874   $213.99   $214.00   $214.00  
  7 purchase totals = $1,124.23       $1,196.0918   $1,196.11   $1,196.10   $1,196.20