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 $57.92   7.298%   $62.147   $62.15   $62.15   $62.10  
  Purchase #2 $103.73   9.369%   $113.4485   $113.45   $113.45   $113.40  
  Purchase #3 $162.28   5.611%   $171.3855   $171.39   $171.40   $171.40  
  Purchase #4 $202.42   7.513%   $217.6278   $217.63   $217.65   $217.60  
  Purchase #5 $189.49   7.725%   $204.1281   $204.13   $204.15   $204.10  
  Purchase #6 $237.56   10.460%   $262.4088   $262.41   $262.40   $262.40  
  Purchase #7 $183.98   4.760%   $192.7374   $192.74   $192.75   $192.70  
  7 purchase totals = $1,137.38       $1,223.8831   $1,223.90   $1,223.95   $1,223.70