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 $116.78   7.784%   $125.8702   $125.87   $125.85   $125.90  
  Purchase #2 $174.54   10.578%   $193.0028   $193.00   $193.00   $193.00  
  Purchase #3 $201.36   7.786%   $217.0379   $217.04   $217.05   $217.00  
  Purchase #4 $138.73   12.177%   $155.6232   $155.62   $155.60   $155.60  
  Purchase #5 $82.95   10.349%   $91.5345   $91.53   $91.55   $91.50  
  Purchase #6 $118.61   11.706%   $132.4945   $132.49   $132.50   $132.50  
  Purchase #7 $121.42   11.410%   $135.274   $135.27   $135.25   $135.30  
  7 purchase totals = $954.39       $1,050.8371   $1,050.82   $1,050.80   $1,050.80