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 $237.32   10.873%   $263.1238   $263.12   $263.10   $263.10  
  Purchase #2 $63.99   5.222%   $67.3316   $67.33   $67.35   $67.30  
  Purchase #3 $41.51   5.665%   $43.8615   $43.86   $43.85   $43.90  
  Purchase #4 $115.64   9.688%   $126.8432   $126.84   $126.85   $126.80  
  Purchase #5 $36.63   7.371%   $39.33   $39.33   $39.35   $39.30  
  Purchase #6 $34.27   5.260%   $36.0726   $36.07   $36.05   $36.10  
  Purchase #7 $103.54   10.785%   $114.7068   $114.71   $114.70   $114.70  
  7 purchase totals = $632.90       $691.2695   $691.26   $691.25   $691.20