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 $86.30   8.545%   $93.6743   $93.67   $93.65   $93.70  
  Purchase #2 $249.54   3.474%   $258.209   $258.21   $258.20   $258.20  
  Purchase #3 $60.49   6.306%   $64.3045   $64.30   $64.30   $64.30  
  Purchase #4 $101.94   7.472%   $109.557   $109.56   $109.55   $109.60  
  Purchase #5 $62.62   6.161%   $66.478   $66.48   $66.50   $66.50  
  Purchase #6 $114.34   4.593%   $119.5916   $119.59   $119.60   $119.60  
  Purchase #7 $194.83   13.123%   $220.3975   $220.40   $220.40   $220.40  
  7 purchase totals = $870.06       $932.2119   $932.21   $932.20   $932.30