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 $70.83   7.458%   $76.1125   $76.11   $76.10   $76.10  
  Purchase #2 $158.88   9.109%   $173.3524   $173.35   $173.35   $173.40  
  Purchase #3 $174.48   5.137%   $183.443   $183.44   $183.45   $183.40  
  Purchase #4 $206.86   5.299%   $217.8215   $217.82   $217.80   $217.80  
  Purchase #5 $57.73   5.639%   $60.9854   $60.99   $61.00   $61.00  
  Purchase #6 $88.26   4.354%   $92.1028   $92.10   $92.10   $92.10  
  Purchase #7 $126.66   10.570%   $140.048   $140.05   $140.05   $140.00  
  7 purchase totals = $883.70       $943.8656   $943.86   $943.85   $943.80