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 $243.93   8.153%   $263.8176   $263.82   $263.80   $263.80  
  Purchase #2 $44.62   3.617%   $46.2339   $46.23   $46.25   $46.20  
  Purchase #3 $97.83   4.241%   $101.979   $101.98   $102.00   $102.00  
  Purchase #4 $47.47   7.836%   $51.1897   $51.19   $51.20   $51.20  
  Purchase #5 $148.55   8.606%   $161.3342   $161.33   $161.35   $161.30  
  Purchase #6 $115.92   8.309%   $125.5518   $125.55   $125.55   $125.60  
  Purchase #7 $189.42   4.121%   $197.226   $197.23   $197.25   $197.20  
  7 purchase totals = $887.74       $947.3322   $947.33   $947.40   $947.30