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 $127.73   10.491%   $141.1302   $141.13   $141.15   $141.10  
  Purchase #2 $152.34   6.703%   $162.5514   $162.55   $162.55   $162.60  
  Purchase #3 $157.96   11.852%   $176.6814   $176.68   $176.70   $176.70  
  Purchase #4 $141.70   12.597%   $159.5499   $159.55   $159.55   $159.50  
  Purchase #5 $108.66   4.567%   $113.6225   $113.62   $113.60   $113.60  
  Purchase #6 $206.90   4.259%   $215.7119   $215.71   $215.70   $215.70  
  Purchase #7 $230.86   11.405%   $257.1896   $257.19   $257.20   $257.20  
  7 purchase totals = $1,126.15       $1,226.4369   $1,226.43   $1,226.45   $1,226.40