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 $244.66   7.462%   $262.9165   $262.92   $262.90   $262.90  
  Purchase #2 $234.51   7.856%   $252.9331   $252.93   $252.95   $252.90  
  Purchase #3 $34.50   7.432%   $37.064   $37.06   $37.05   $37.10  
  Purchase #4 $118.94   11.181%   $132.2387   $132.24   $132.25   $132.20  
  Purchase #5 $224.66   8.274%   $243.2484   $243.25   $243.25   $243.20  
  Purchase #6 $242.60   8.246%   $262.6048   $262.60   $262.60   $262.60  
  Purchase #7 $234.93   10.799%   $260.3001   $260.30   $260.30   $260.30  
  7 purchase totals = $1,334.80       $1,451.3056   $1,451.30   $1,451.30   $1,451.20