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 $57.65   5.734%   $60.9557   $60.96   $60.95   $61.00  
  Purchase #2 $108.54   6.230%   $115.302   $115.30   $115.30   $115.30  
  Purchase #3 $126.72   4.412%   $132.3109   $132.31   $132.30   $132.30  
  Purchase #4 $236.34   11.431%   $263.356   $263.36   $263.35   $263.40  
  Purchase #5 $14.63   13.245%   $16.5677   $16.57   $16.55   $16.60  
  Purchase #6 $127.67   3.282%   $131.8601   $131.86   $131.85   $131.90  
  Purchase #7 $224.42   5.806%   $237.4498   $237.45   $237.45   $237.40  
  7 purchase totals = $895.97       $957.8022   $957.81   $957.75   $957.90