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 $119.91   5.284%   $126.246   $126.25   $126.25   $126.20  
  Purchase #2 $116.33   7.774%   $125.3735   $125.37   $125.35   $125.40  
  Purchase #3 $13.40   13.616%   $15.2245   $15.22   $15.20   $15.20  
  Purchase #4 $160.63   9.323%   $175.6055   $175.61   $175.60   $175.60  
  Purchase #5 $234.27   5.732%   $247.6984   $247.70   $247.70   $247.70  
  Purchase #6 $228.67   5.728%   $241.7682   $241.77   $241.75   $241.80  
  Purchase #7 $50.42   10.316%   $55.6213   $55.62   $55.60   $55.60  
  7 purchase totals = $923.63       $987.5374   $987.54   $987.45   $987.50