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 $232.44   6.248%   $246.9629   $246.96   $246.95   $247.00  
  Purchase #2 $228.51   3.463%   $236.4233   $236.42   $236.40   $236.40  
  Purchase #3 $94.28   11.236%   $104.8733   $104.87   $104.85   $104.90  
  Purchase #4 $219.41   11.665%   $245.0042   $245.00   $245.00   $245.00  
  Purchase #5 $153.92   11.717%   $171.9548   $171.95   $171.95   $172.00  
  Purchase #6 $191.34   4.705%   $200.3425   $200.34   $200.35   $200.30  
  Purchase #7 $234.61   13.536%   $266.3668   $266.37   $266.35   $266.40  
  7 purchase totals = $1,354.51       $1,471.9278   $1,471.91   $1,471.85   $1,472.00