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 $55.99   9.592%   $61.3606   $61.36   $61.35   $61.40  
  Purchase #2 $23.90   9.718%   $26.2226   $26.22   $26.20   $26.20  
  Purchase #3 $11.64   11.845%   $13.0188   $13.02   $13.00   $13.00  
  Purchase #4 $176.64   10.727%   $195.5882   $195.59   $195.60   $195.60  
  Purchase #5 $217.58   3.429%   $225.0408   $225.04   $225.05   $225.00  
  Purchase #6 $224.74   10.787%   $248.9827   $248.98   $249.00   $249.00  
  Purchase #7 $10.73   7.112%   $11.4931   $11.49   $11.50   $11.50  
  7 purchase totals = $721.22       $781.7068   $781.70   $781.70   $781.70