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 $43.67   11.632%   $48.7497   $48.75   $48.75   $48.70  
  Purchase #2 $212.86   12.690%   $239.8719   $239.87   $239.85   $239.90  
  Purchase #3 $125.42   6.434%   $133.4895   $133.49   $133.50   $133.50  
  Purchase #4 $163.78   11.766%   $183.0504   $183.05   $183.05   $183.10  
  Purchase #5 $191.60   5.757%   $202.6304   $202.63   $202.65   $202.60  
  Purchase #6 $209.96   12.162%   $235.4953   $235.50   $235.50   $235.50  
  Purchase #7 $146.91   3.330%   $151.8021   $151.80   $151.80   $151.80  
  7 purchase totals = $1,094.20       $1,195.0893   $1,195.09   $1,195.10   $1,195.10