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 $55.38   12.497%   $62.3008   $62.30   $62.30   $62.30  
  Purchase #2 $156.62   5.769%   $165.6554   $165.66   $165.65   $165.70  
  Purchase #3 $71.36   4.349%   $74.4634   $74.46   $74.45   $74.50  
  Purchase #4 $193.26   10.520%   $213.591   $213.59   $213.60   $213.60  
  Purchase #5 $224.30   5.193%   $235.9479   $235.95   $235.95   $235.90  
  Purchase #6 $92.76   9.607%   $101.6715   $101.67   $101.65   $101.70  
  Purchase #7 $108.61   3.867%   $112.8099   $112.81   $112.80   $112.80  
  7 purchase totals = $902.29       $966.4399   $966.44   $966.40   $966.50