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 $53.42   12.578%   $60.1392   $60.14   $60.15   $60.10  
  Purchase #2 $161.46   7.754%   $173.9796   $173.98   $174.00   $174.00  
  Purchase #3 $241.74   12.438%   $271.8076   $271.81   $271.80   $271.80  
  Purchase #4 $205.52   6.515%   $218.9096   $218.91   $218.90   $218.90  
  Purchase #5 $146.44   10.621%   $161.9934   $161.99   $162.00   $162.00  
  Purchase #6 $71.46   6.633%   $76.1999   $76.20   $76.20   $76.20  
  Purchase #7 $195.27   9.315%   $213.4594   $213.46   $213.45   $213.50  
  7 purchase totals = $1,075.31       $1,176.4887   $1,176.49   $1,176.50   $1,176.50