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 $59.35   5.510%   $62.6202   $62.62   $62.60   $62.60  
  Purchase #2 $216.30   9.610%   $237.0864   $237.09   $237.10   $237.10  
  Purchase #3 $86.64   6.533%   $92.3002   $92.30   $92.30   $92.30  
  Purchase #4 $132.79   5.750%   $140.4254   $140.43   $140.45   $140.40  
  Purchase #5 $215.39   8.258%   $233.1769   $233.18   $233.20   $233.20  
  Purchase #6 $19.75   3.428%   $20.427   $20.43   $20.45   $20.40  
  Purchase #7 $43.64   8.759%   $47.4624   $47.46   $47.45   $47.50  
  7 purchase totals = $773.86       $833.4985   $833.51   $833.55   $833.50