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 $102.95   10.548%   $113.8092   $113.81   $113.80   $113.80  
  Purchase #2 $51.65   7.192%   $55.3647   $55.36   $55.35   $55.40  
  Purchase #3 $219.56   4.435%   $229.2975   $229.30   $229.30   $229.30  
  Purchase #4 $43.87   9.793%   $48.1662   $48.17   $48.15   $48.20  
  Purchase #5 $109.97   6.661%   $117.2951   $117.30   $117.30   $117.30  
  Purchase #6 $61.69   5.841%   $65.2933   $65.29   $65.30   $65.30  
  Purchase #7 $125.54   3.279%   $129.6565   $129.66   $129.65   $129.70  
  7 purchase totals = $715.23       $758.8825   $758.89   $758.85   $759.00