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 $82.88   13.692%   $94.2279   $94.23   $94.25   $94.20  
  Purchase #2 $213.67   13.209%   $241.8937   $241.89   $241.90   $241.90  
  Purchase #3 $239.78   5.806%   $253.7016   $253.70   $253.70   $253.70  
  Purchase #4 $136.62   11.359%   $152.1387   $152.14   $152.15   $152.10  
  Purchase #5 $236.50   10.792%   $262.0231   $262.02   $262.00   $262.00  
  Purchase #6 $188.99   7.596%   $203.3457   $203.35   $203.35   $203.30  
  Purchase #7 $163.38   4.125%   $170.1194   $170.12   $170.10   $170.10  
  7 purchase totals = $1,261.82       $1,377.4501   $1,377.45   $1,377.45   $1,377.30