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 $61.26   9.425%   $67.0338   $67.03   $67.05   $67.00  
  Purchase #2 $144.40   5.272%   $152.0128   $152.01   $152.00   $152.00  
  Purchase #3 $36.78   13.158%   $41.6195   $41.62   $41.60   $41.60  
  Purchase #4 $229.95   3.163%   $237.2233   $237.22   $237.20   $237.20  
  Purchase #5 $81.75   7.776%   $88.1069   $88.11   $88.10   $88.10  
  Purchase #6 $108.57   5.548%   $114.5935   $114.59   $114.60   $114.60  
  Purchase #7 $30.92   6.812%   $33.0263   $33.03   $33.05   $33.00  
  7 purchase totals = $693.63       $733.6161   $733.61   $733.60   $733.50