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 $183.75   7.471%   $197.478   $197.48   $197.50   $197.50  
  Purchase #2 $126.36   3.464%   $130.7371   $130.74   $130.75   $130.70  
  Purchase #3 $59.93   3.317%   $61.9179   $61.92   $61.90   $61.90  
  Purchase #4 $187.77   3.624%   $194.5748   $194.57   $194.55   $194.60  
  Purchase #5 $249.63   11.857%   $279.2286   $279.23   $279.25   $279.20  
  Purchase #6 $202.54   13.509%   $229.9011   $229.90   $229.90   $229.90  
  Purchase #7 $247.73   5.550%   $261.479   $261.48   $261.50   $261.50  
  7 purchase totals = $1,257.71       $1,355.3165   $1,355.32   $1,355.35   $1,355.30