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 $65.39   9.475%   $71.5857   $71.59   $71.60   $71.60  
  Purchase #2 $118.86   6.531%   $126.6227   $126.62   $126.60   $126.60  
  Purchase #3 $164.46   12.203%   $184.5291   $184.53   $184.55   $184.50  
  Purchase #4 $192.61   7.585%   $207.2195   $207.22   $207.20   $207.20  
  Purchase #5 $85.80   9.622%   $94.0557   $94.06   $94.05   $94.10  
  Purchase #6 $155.66   13.185%   $176.1838   $176.18   $176.20   $176.20  
  Purchase #7 $174.37   5.845%   $184.5619   $184.56   $184.55   $184.60  
  7 purchase totals = $957.15       $1,044.7584   $1,044.76   $1,044.75   $1,044.80