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 $95.29   10.167%   $104.9781   $104.98   $105.00   $105.00  
  Purchase #2 $195.47   6.170%   $207.5305   $207.53   $207.55   $207.50  
  Purchase #3 $47.53   5.684%   $50.2316   $50.23   $50.25   $50.20  
  Purchase #4 $195.86   7.667%   $210.8766   $210.88   $210.90   $210.90  
  Purchase #5 $87.88   9.286%   $96.0405   $96.04   $96.05   $96.00  
  Purchase #6 $184.69   4.577%   $193.1433   $193.14   $193.15   $193.10  
  Purchase #7 $88.83   4.566%   $92.886   $92.89   $92.90   $92.90  
  7 purchase totals = $895.55       $955.6866   $955.69   $955.80   $955.60