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 $86.95   11.131%   $96.6284   $96.63   $96.65   $96.60  
  Purchase #2 $92.35   5.326%   $97.2686   $97.27   $97.25   $97.30  
  Purchase #3 $132.39   11.746%   $147.9405   $147.94   $147.95   $147.90  
  Purchase #4 $222.53   9.288%   $243.1986   $243.20   $243.20   $243.20  
  Purchase #5 $194.51   10.765%   $215.449   $215.45   $215.45   $215.40  
  Purchase #6 $66.96   7.849%   $72.2157   $72.22   $72.20   $72.20  
  Purchase #7 $64.34   9.814%   $70.6543   $70.65   $70.65   $70.70  
  7 purchase totals = $860.03       $943.3551   $943.36   $943.35   $943.30