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 $57.42   9.290%   $62.7543   $62.75   $62.75   $62.80  
  Purchase #2 $245.50   5.461%   $258.9068   $258.91   $258.90   $258.90  
  Purchase #3 $51.30   12.339%   $57.6299   $57.63   $57.65   $57.60  
  Purchase #4 $212.66   4.312%   $221.8299   $221.83   $221.85   $221.80  
  Purchase #5 $212.35   8.268%   $229.9071   $229.91   $229.90   $229.90  
  Purchase #6 $224.84   3.441%   $232.5767   $232.58   $232.60   $232.60  
  Purchase #7 $20.84   9.171%   $22.7512   $22.75   $22.75   $22.80  
  7 purchase totals = $1,024.91       $1,086.3559   $1,086.36   $1,086.40   $1,086.40