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 $197.82   4.620%   $206.9593   $206.96   $206.95   $207.00  
  Purchase #2 $64.99   7.631%   $69.9494   $69.95   $69.95   $69.90  
  Purchase #3 $67.49   7.291%   $72.4107   $72.41   $72.40   $72.40  
  Purchase #4 $233.70   3.453%   $241.7697   $241.77   $241.75   $241.80  
  Purchase #5 $38.38   5.366%   $40.4395   $40.44   $40.45   $40.40  
  Purchase #6 $62.83   8.653%   $68.2667   $68.27   $68.25   $68.30  
  Purchase #7 $27.25   6.499%   $29.021   $29.02   $29.00   $29.00  
  7 purchase totals = $692.46       $728.8163   $728.82   $728.75   $728.80