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 $250.42   5.295%   $263.6797   $263.68   $263.70   $263.70  
  Purchase #2 $215.46   5.355%   $226.9979   $227.00   $227.00   $227.00  
  Purchase #3 $44.71   3.804%   $46.4108   $46.41   $46.40   $46.40  
  Purchase #4 $185.63   5.134%   $195.1602   $195.16   $195.15   $195.20  
  Purchase #5 $46.51   10.228%   $51.267   $51.27   $51.25   $51.30  
  Purchase #6 $85.50   9.188%   $93.3557   $93.36   $93.35   $93.40  
  Purchase #7 $168.58   8.836%   $183.4757   $183.48   $183.50   $183.50  
  7 purchase totals = $996.81       $1,060.3470   $1,060.36   $1,060.35   $1,060.50