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 $60.41   3.670%   $62.627   $62.63   $62.65   $62.60  
  Purchase #2 $182.64   13.640%   $207.5521   $207.55   $207.55   $207.60  
  Purchase #3 $6.93   8.662%   $7.5303   $7.53   $7.55   $7.50  
  Purchase #4 $103.69   12.609%   $116.7643   $116.76   $116.75   $116.80  
  Purchase #5 $33.93   12.747%   $38.2551   $38.26   $38.25   $38.30  
  Purchase #6 $185.33   4.851%   $194.3204   $194.32   $194.30   $194.30  
  Purchase #7 $147.60   9.187%   $161.16   $161.16   $161.15   $161.20  
  7 purchase totals = $720.53       $788.2092   $788.21   $788.20   $788.30