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 $219.82   5.826%   $232.6267   $232.63   $232.65   $232.60  
  Purchase #2 $226.56   4.262%   $236.216   $236.22   $236.20   $236.20  
  Purchase #3 $47.41   8.692%   $51.5309   $51.53   $51.55   $51.50  
  Purchase #4 $60.26   3.341%   $62.2733   $62.27   $62.25   $62.30  
  Purchase #5 $42.70   3.755%   $44.3034   $44.30   $44.30   $44.30  
  Purchase #6 $53.83   11.494%   $60.0172   $60.02   $60.00   $60.00  
  Purchase #7 $213.29   6.140%   $226.386   $226.39   $226.40   $226.40  
  7 purchase totals = $863.87       $913.3535   $913.36   $913.35   $913.30