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 $10.34   4.840%   $10.8405   $10.84   $10.85   $10.80  
  Purchase #2 $141.25   8.794%   $153.6715   $153.67   $153.65   $153.70  
  Purchase #3 $72.36   5.281%   $76.1813   $76.18   $76.20   $76.20  
  Purchase #4 $232.26   10.769%   $257.2721   $257.27   $257.25   $257.30  
  Purchase #5 $148.49   9.502%   $162.5995   $162.60   $162.60   $162.60  
  Purchase #6 $197.83   6.434%   $210.5584   $210.56   $210.55   $210.60  
  Purchase #7 $168.97   4.684%   $176.8846   $176.88   $176.90   $176.90  
  7 purchase totals = $971.50       $1,048.0079   $1,048.00   $1,048.00   $1,048.10