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 $92.86   7.258%   $99.5998   $99.60   $99.60   $99.60  
  Purchase #2 $168.25   11.457%   $187.5264   $187.53   $187.55   $187.50  
  Purchase #3 $76.52   9.752%   $83.9822   $83.98   $84.00   $84.00  
  Purchase #4 $39.56   4.779%   $41.4506   $41.45   $41.45   $41.50  
  Purchase #5 $211.40   11.344%   $235.3812   $235.38   $235.40   $235.40  
  Purchase #6 $116.30   7.541%   $125.0702   $125.07   $125.05   $125.10  
  Purchase #7 $182.76   6.794%   $195.1767   $195.18   $195.20   $195.20  
  7 purchase totals = $887.65       $968.1871   $968.19   $968.25   $968.30