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 $53.65   9.228%   $58.6008   $58.60   $58.60   $58.60  
  Purchase #2 $117.26   7.543%   $126.1049   $126.10   $126.10   $126.10  
  Purchase #3 $154.41   9.870%   $169.6503   $169.65   $169.65   $169.70  
  Purchase #4 $112.97   6.805%   $120.6576   $120.66   $120.65   $120.70  
  Purchase #5 $42.66   4.873%   $44.7388   $44.74   $44.75   $44.70  
  Purchase #6 $152.35   10.589%   $168.4823   $168.48   $168.50   $168.50  
  Purchase #7 $62.36   13.830%   $70.9844   $70.98   $71.00   $71.00  
  7 purchase totals = $695.66       $759.2191   $759.21   $759.25   $759.30