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 $57.98   8.197%   $62.7326   $62.73   $62.75   $62.70  
  Purchase #2 $224.71   8.603%   $244.0418   $244.04   $244.05   $244.00  
  Purchase #3 $206.96   5.170%   $217.6598   $217.66   $217.65   $217.70  
  Purchase #4 $166.42   11.429%   $185.4401   $185.44   $185.45   $185.40  
  Purchase #5 $54.61   7.426%   $58.6653   $58.67   $58.65   $58.70  
  Purchase #6 $145.76   12.362%   $163.7789   $163.78   $163.80   $163.80  
  Purchase #7 $141.83   8.752%   $154.243   $154.24   $154.25   $154.20  
  7 purchase totals = $998.27       $1,086.5615   $1,086.56   $1,086.60   $1,086.50