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 $87.58   9.245%   $95.6768   $95.68   $95.70   $95.70  
  Purchase #2 $121.90   9.517%   $133.5012   $133.50   $133.50   $133.50  
  Purchase #3 $22.89   11.823%   $25.5963   $25.60   $25.60   $25.60  
  Purchase #4 $213.47   6.686%   $227.7426   $227.74   $227.75   $227.70  
  Purchase #5 $81.51   4.569%   $85.2342   $85.23   $85.25   $85.20  
  Purchase #6 $245.30   13.805%   $279.1637   $279.16   $279.15   $279.20  
  Purchase #7 $171.67   9.103%   $187.2971   $187.30   $187.30   $187.30  
  7 purchase totals = $944.32       $1,034.2119   $1,034.21   $1,034.25   $1,034.20