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 $64.53   9.413%   $70.6042   $70.60   $70.60   $70.60  
  Purchase #2 $114.96   7.166%   $123.198   $123.20   $123.20   $123.20  
  Purchase #3 $19.53   5.220%   $20.5495   $20.55   $20.55   $20.50  
  Purchase #4 $123.92   5.529%   $130.7715   $130.77   $130.75   $130.80  
  Purchase #5 $217.26   4.798%   $227.6841   $227.68   $227.70   $227.70  
  Purchase #6 $212.56   9.575%   $232.9126   $232.91   $232.90   $232.90  
  Purchase #7 $112.79   5.600%   $119.1062   $119.11   $119.10   $119.10  
  7 purchase totals = $865.55       $924.8261   $924.82   $924.80   $924.80