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 $119.63   5.284%   $125.9512   $125.95   $125.95   $126.00  
  Purchase #2 $134.75   11.864%   $150.7367   $150.74   $150.75   $150.70  
  Purchase #3 $11.45   3.583%   $11.8603   $11.86   $11.85   $11.90  
  Purchase #4 $250.69   11.616%   $279.8102   $279.81   $279.80   $279.80  
  Purchase #5 $168.46   3.242%   $173.9215   $173.92   $173.90   $173.90  
  Purchase #6 $121.67   9.763%   $133.5486   $133.55   $133.55   $133.50  
  Purchase #7 $195.67   8.575%   $212.4487   $212.45   $212.45   $212.40  
  7 purchase totals = $1,002.32       $1,088.2772   $1,088.28   $1,088.25   $1,088.20