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 $69.90   7.298%   $75.0013   $75.00   $75.00   $75.00  
  Purchase #2 $154.98   10.541%   $171.3164   $171.32   $171.30   $171.30  
  Purchase #3 $40.55   6.439%   $43.161   $43.16   $43.15   $43.20  
  Purchase #4 $108.98   10.727%   $120.6703   $120.67   $120.65   $120.70  
  Purchase #5 $165.28   3.273%   $170.6896   $170.69   $170.70   $170.70  
  Purchase #6 $125.64   12.422%   $141.247   $141.25   $141.25   $141.20  
  Purchase #7 $10.49   7.620%   $11.2893   $11.29   $11.30   $11.30  
  7 purchase totals = $675.82       $733.3749   $733.38   $733.35   $733.40