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 $63.73   13.374%   $72.2533   $72.25   $72.25   $72.30  
  Purchase #2 $234.84   3.358%   $242.7259   $242.73   $242.75   $242.70  
  Purchase #3 $242.70   10.574%   $268.3631   $268.36   $268.35   $268.40  
  Purchase #4 $93.48   5.797%   $98.899   $98.90   $98.90   $98.90  
  Purchase #5 $232.36   5.517%   $245.1793   $245.18   $245.20   $245.20  
  Purchase #6 $114.90   6.171%   $121.9905   $121.99   $122.00   $122.00  
  Purchase #7 $217.94   7.717%   $234.7584   $234.76   $234.75   $234.80  
  7 purchase totals = $1,199.95       $1,284.1695   $1,284.17   $1,284.20   $1,284.30