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 $91.74   4.588%   $95.949   $95.95   $95.95   $95.90  
  Purchase #2 $85.70   7.809%   $92.3923   $92.39   $92.40   $92.40  
  Purchase #3 $12.34   12.708%   $13.9082   $13.91   $13.90   $13.90  
  Purchase #4 $201.49   4.282%   $210.1178   $210.12   $210.10   $210.10  
  Purchase #5 $235.67   5.863%   $249.4873   $249.49   $249.50   $249.50  
  Purchase #6 $241.71   6.860%   $258.2913   $258.29   $258.30   $258.30  
  Purchase #7 $15.60   8.355%   $16.9034   $16.90   $16.90   $16.90  
  7 purchase totals = $884.25       $937.0493   $937.05   $937.05   $937.00