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 $55.76   9.522%   $61.0695   $61.07   $61.05   $61.10  
  Purchase #2 $32.52   4.740%   $34.0614   $34.06   $34.05   $34.10  
  Purchase #3 $91.73   9.821%   $100.7388   $100.74   $100.75   $100.70  
  Purchase #4 $151.68   3.644%   $157.2072   $157.21   $157.20   $157.20  
  Purchase #5 $69.78   9.418%   $76.3519   $76.35   $76.35   $76.40  
  Purchase #6 $33.48   7.155%   $35.8755   $35.88   $35.90   $35.90  
  Purchase #7 $249.84   7.404%   $268.3382   $268.34   $268.35   $268.30  
  7 purchase totals = $684.79       $733.6425   $733.65   $733.65   $733.70