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 $41.84   11.661%   $46.719   $46.72   $46.70   $46.70  
  Purchase #2 $100.60   11.835%   $112.506   $112.51   $112.50   $112.50  
  Purchase #3 $111.71   3.599%   $115.7304   $115.73   $115.75   $115.70  
  Purchase #4 $144.29   13.434%   $163.6739   $163.67   $163.65   $163.70  
  Purchase #5 $157.45   3.181%   $162.4585   $162.46   $162.45   $162.50  
  Purchase #6 $47.53   10.152%   $52.3552   $52.36   $52.35   $52.40  
  Purchase #7 $94.84   3.807%   $98.4506   $98.45   $98.45   $98.50  
  7 purchase totals = $698.26       $751.8936   $751.90   $751.85   $752.00