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 $187.45   9.648%   $205.5352   $205.54   $205.55   $205.50  
  Purchase #2 $44.97   5.207%   $47.3116   $47.31   $47.30   $47.30  
  Purchase #3 $60.70   12.867%   $68.5103   $68.51   $68.50   $68.50  
  Purchase #4 $236.51   5.651%   $249.8752   $249.88   $249.90   $249.90  
  Purchase #5 $69.64   9.186%   $76.0371   $76.04   $76.05   $76.00  
  Purchase #6 $88.28   4.603%   $92.3435   $92.34   $92.35   $92.30  
  Purchase #7 $130.86   11.662%   $146.1209   $146.12   $146.10   $146.10  
  7 purchase totals = $818.41       $885.7338   $885.74   $885.75   $885.60