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   7.137%   $62.0538   $62.05   $62.05   $62.10  
  Purchase #2 $146.88   8.400%   $159.2179   $159.22   $159.20   $159.20  
  Purchase #3 $109.26   9.116%   $119.2201   $119.22   $119.20   $119.20  
  Purchase #4 $195.94   6.291%   $208.2666   $208.27   $208.25   $208.30  
  Purchase #5 $98.89   12.854%   $111.6013   $111.60   $111.60   $111.60  
  Purchase #6 $238.58   12.280%   $267.8776   $267.88   $267.90   $267.90  
  Purchase #7 $90.72   6.782%   $96.8726   $96.87   $96.85   $96.90  
  7 purchase totals = $938.19       $1,025.1099   $1,025.11   $1,025.05   $1,025.20