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 $212.78   9.288%   $232.543   $232.54   $232.55   $232.50  
  Purchase #2 $58.89   6.275%   $62.5853   $62.59   $62.60   $62.60  
  Purchase #3 $205.71   3.667%   $213.2534   $213.25   $213.25   $213.30  
  Purchase #4 $175.31   10.528%   $193.7666   $193.77   $193.75   $193.80  
  Purchase #5 $96.31   8.264%   $104.2691   $104.27   $104.25   $104.30  
  Purchase #6 $189.27   9.687%   $207.6046   $207.60   $207.60   $207.60  
  Purchase #7 $178.82   6.663%   $190.7348   $190.73   $190.75   $190.70  
  7 purchase totals = $1,117.09       $1,204.7568   $1,204.75   $1,204.75   $1,204.80