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 $182.63   7.480%   $196.2907   $196.29   $196.30   $196.30  
  Purchase #2 $248.74   7.606%   $267.6592   $267.66   $267.65   $267.70  
  Purchase #3 $176.41   9.806%   $193.7088   $193.71   $193.70   $193.70  
  Purchase #4 $136.70   11.809%   $152.8429   $152.84   $152.85   $152.80  
  Purchase #5 $121.80   5.496%   $128.4941   $128.49   $128.50   $128.50  
  Purchase #6 $6.87   7.716%   $7.4001   $7.40   $7.40   $7.40  
  Purchase #7 $65.73   3.743%   $68.1903   $68.19   $68.20   $68.20  
  7 purchase totals = $938.88       $1,014.5861   $1,014.58   $1,014.60   $1,014.60