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 $210.27   12.407%   $236.3582   $236.36   $236.35   $236.40  
  Purchase #2 $93.93   7.862%   $101.3148   $101.31   $101.30   $101.30  
  Purchase #3 $51.60   3.594%   $53.4545   $53.45   $53.45   $53.50  
  Purchase #4 $55.90   6.622%   $59.6017   $59.60   $59.60   $59.60  
  Purchase #5 $229.32   4.669%   $240.027   $240.03   $240.05   $240.00  
  Purchase #6 $234.91   10.827%   $260.3437   $260.34   $260.35   $260.30  
  Purchase #7 $60.30   5.210%   $63.4416   $63.44   $63.45   $63.40  
  7 purchase totals = $936.23       $1,014.5415   $1,014.53   $1,014.55   $1,014.50