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 $58.67   7.214%   $62.9025   $62.90   $62.90   $62.90  
  Purchase #2 $221.50   3.393%   $229.0155   $229.02   $229.00   $229.00  
  Purchase #3 $157.36   8.373%   $170.5358   $170.54   $170.55   $170.50  
  Purchase #4 $211.90   3.242%   $218.7698   $218.77   $218.75   $218.80  
  Purchase #5 $66.41   3.494%   $68.7304   $68.73   $68.75   $68.70  
  Purchase #6 $14.39   6.171%   $15.278   $15.28   $15.30   $15.30  
  Purchase #7 $182.59   8.643%   $198.3713   $198.37   $198.35   $198.40  
  7 purchase totals = $912.82       $963.6033   $963.61   $963.60   $963.60