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 $227.30   4.689%   $237.9581   $237.96   $237.95   $238.00  
  Purchase #2 $226.39   3.156%   $233.5349   $233.53   $233.55   $233.50  
  Purchase #3 $240.77   13.497%   $273.2667   $273.27   $273.25   $273.30  
  Purchase #4 $216.32   4.532%   $226.1236   $226.12   $226.10   $226.10  
  Purchase #5 $19.34   9.490%   $21.1754   $21.18   $21.20   $21.20  
  Purchase #6 $213.86   10.502%   $236.3196   $236.32   $236.30   $236.30  
  Purchase #7 $226.99   4.174%   $236.4646   $236.46   $236.45   $236.50  
  7 purchase totals = $1,370.97       $1,464.8429   $1,464.84   $1,464.80   $1,464.90