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 $176.72   10.771%   $195.7545   $195.75   $195.75   $195.80  
  Purchase #2 $92.55   4.395%   $96.6176   $96.62   $96.60   $96.60  
  Purchase #3 $205.48   5.674%   $217.1389   $217.14   $217.15   $217.10  
  Purchase #4 $156.46   4.462%   $163.4412   $163.44   $163.45   $163.40  
  Purchase #5 $234.50   4.117%   $244.1544   $244.15   $244.15   $244.20  
  Purchase #6 $157.35   11.498%   $175.4421   $175.44   $175.45   $175.40  
  Purchase #7 $126.39   12.548%   $142.2494   $142.25   $142.25   $142.20  
  7 purchase totals = $1,149.45       $1,234.7981   $1,234.79   $1,234.80   $1,234.70