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 $87.31   10.117%   $96.1432   $96.14   $96.15   $96.10  
  Purchase #2 $161.28   11.353%   $179.5901   $179.59   $179.60   $179.60  
  Purchase #3 $63.27   8.664%   $68.7517   $68.75   $68.75   $68.80  
  Purchase #4 $90.59   11.668%   $101.16   $101.16   $101.15   $101.20  
  Purchase #5 $97.83   10.120%   $107.7304   $107.73   $107.75   $107.70  
  Purchase #6 $6.66   7.828%   $7.1813   $7.18   $7.20   $7.20  
  Purchase #7 $167.46   3.347%   $173.0649   $173.06   $173.05   $173.10  
  7 purchase totals = $674.40       $733.6216   $733.61   $733.65   $733.70