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 $113.73   10.741%   $125.9457   $125.95   $125.95   $125.90  
  Purchase #2 $87.95   8.308%   $95.2569   $95.26   $95.25   $95.30  
  Purchase #3 $90.79   3.874%   $94.3072   $94.31   $94.30   $94.30  
  Purchase #4 $69.31   7.167%   $74.2774   $74.28   $74.30   $74.30  
  Purchase #5 $5.98   7.342%   $6.4191   $6.42   $6.40   $6.40  
  Purchase #6 $32.53   10.425%   $35.9213   $35.92   $35.90   $35.90  
  Purchase #7 $128.75   3.729%   $133.5511   $133.55   $133.55   $133.60  
  7 purchase totals = $529.04       $565.6787   $565.69   $565.65   $565.70