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 $60.42   12.590%   $68.0269   $68.03   $68.05   $68.00  
  Purchase #2 $173.57   7.119%   $185.9264   $185.93   $185.95   $185.90  
  Purchase #3 $214.57   8.156%   $232.0703   $232.07   $232.05   $232.10  
  Purchase #4 $241.63   7.777%   $260.4216   $260.42   $260.40   $260.40  
  Purchase #5 $148.37   12.188%   $166.4533   $166.45   $166.45   $166.50  
  Purchase #6 $133.38   6.327%   $141.819   $141.82   $141.80   $141.80  
  Purchase #7 $196.64   4.639%   $205.7621   $205.76   $205.75   $205.80  
  7 purchase totals = $1,168.58       $1,260.4796   $1,260.48   $1,260.45   $1,260.50