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 $244.66   8.820%   $266.239   $266.24   $266.25   $266.20  
  Purchase #2 $124.27   5.235%   $130.7755   $130.78   $130.80   $130.80  
  Purchase #3 $169.93   10.199%   $187.2612   $187.26   $187.25   $187.30  
  Purchase #4 $99.46   12.622%   $112.0138   $112.01   $112.00   $112.00  
  Purchase #5 $61.54   10.490%   $67.9955   $68.00   $68.00   $68.00  
  Purchase #6 $209.93   10.275%   $231.5003   $231.50   $231.50   $231.50  
  Purchase #7 $104.92   7.355%   $112.6369   $112.64   $112.65   $112.60  
  7 purchase totals = $1,014.71       $1,108.4222   $1,108.43   $1,108.45   $1,108.40