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 $58.51   4.696%   $61.2576   $61.26   $61.25   $61.30  
  Purchase #2 $118.56   6.584%   $126.366   $126.37   $126.35   $126.40  
  Purchase #3 $24.78   3.383%   $25.6183   $25.62   $25.60   $25.60  
  Purchase #4 $183.73   7.731%   $197.9342   $197.93   $197.95   $197.90  
  Purchase #5 $60.35   13.373%   $68.4206   $68.42   $68.40   $68.40  
  Purchase #6 $47.47   6.827%   $50.7108   $50.71   $50.70   $50.70  
  Purchase #7 $206.62   4.813%   $216.5646   $216.56   $216.55   $216.60  
  7 purchase totals = $700.02       $746.8721   $746.87   $746.80   $746.90