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 $206.71   9.113%   $225.5475   $225.55   $225.55   $225.50  
  Purchase #2 $35.34   3.718%   $36.6539   $36.65   $36.65   $36.70  
  Purchase #3 $216.98   9.215%   $236.9747   $236.97   $236.95   $237.00  
  Purchase #4 $88.84   12.229%   $99.7042   $99.70   $99.70   $99.70  
  Purchase #5 $212.86   13.332%   $241.2385   $241.24   $241.25   $241.20  
  Purchase #6 $123.92   12.382%   $139.2638   $139.26   $139.25   $139.30  
  Purchase #7 $214.45   6.872%   $229.187   $229.19   $229.20   $229.20  
  7 purchase totals = $1,099.10       $1,208.5696   $1,208.56   $1,208.55   $1,208.60