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 $56.66   8.322%   $61.3752   $61.38   $61.40   $61.40  
  Purchase #2 $67.27   5.581%   $71.0243   $71.02   $71.00   $71.00  
  Purchase #3 $211.26   8.248%   $228.6847   $228.68   $228.70   $228.70  
  Purchase #4 $194.36   12.610%   $218.8688   $218.87   $218.85   $218.90  
  Purchase #5 $69.53   8.730%   $75.6   $75.60   $75.60   $75.60  
  Purchase #6 $10.44   10.419%   $11.5277   $11.53   $11.55   $11.50  
  Purchase #7 $42.26   8.679%   $45.9277   $45.93   $45.95   $45.90  
  7 purchase totals = $651.78       $713.0084   $713.01   $713.05   $713.00