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 $83.75   13.268%   $94.862   $94.86   $94.85   $94.90  
  Purchase #2 $163.39   8.621%   $177.4759   $177.48   $177.50   $177.50  
  Purchase #3 $68.62   5.328%   $72.2761   $72.28   $72.30   $72.30  
  Purchase #4 $127.77   4.398%   $133.3893   $133.39   $133.40   $133.40  
  Purchase #5 $214.28   7.623%   $230.6146   $230.61   $230.60   $230.60  
  Purchase #6 $110.92   7.107%   $118.8031   $118.80   $118.80   $118.80  
  Purchase #7 $113.78   4.730%   $119.1618   $119.16   $119.15   $119.20  
  7 purchase totals = $882.51       $946.5828   $946.58   $946.60   $946.70