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 $117.36   7.343%   $125.9777   $125.98   $126.00   $126.00  
  Purchase #2 $224.25   13.601%   $254.7502   $254.75   $254.75   $254.80  
  Purchase #3 $167.94   7.448%   $180.4482   $180.45   $180.45   $180.40  
  Purchase #4 $64.34   8.274%   $69.6635   $69.66   $69.65   $69.70  
  Purchase #5 $131.42   5.159%   $138.2   $138.20   $138.20   $138.20  
  Purchase #6 $248.39   12.655%   $279.8238   $279.82   $279.80   $279.80  
  Purchase #7 $215.77   10.520%   $238.469   $238.47   $238.45   $238.50  
  7 purchase totals = $1,169.47       $1,287.3324   $1,287.33   $1,287.30   $1,287.40