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 $104.27   3.335%   $107.7474   $107.75   $107.75   $107.70  
  Purchase #2 $190.57   7.517%   $204.8951   $204.90   $204.90   $204.90  
  Purchase #3 $151.38   8.554%   $164.329   $164.33   $164.35   $164.30  
  Purchase #4 $92.56   7.329%   $99.3437   $99.34   $99.35   $99.30  
  Purchase #5 $126.55   5.353%   $133.3242   $133.32   $133.30   $133.30  
  Purchase #6 $21.95   11.673%   $24.5122   $24.51   $24.50   $24.50  
  Purchase #7 $199.61   6.421%   $212.427   $212.43   $212.45   $212.40  
  7 purchase totals = $886.89       $946.5786   $946.58   $946.60   $946.40