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 $89.38   6.624%   $95.3005   $95.30   $95.30   $95.30  
  Purchase #2 $68.66   7.474%   $73.7916   $73.79   $73.80   $73.80  
  Purchase #3 $66.79   4.239%   $69.6212   $69.62   $69.60   $69.60  
  Purchase #4 $19.36   4.543%   $20.2395   $20.24   $20.25   $20.20  
  Purchase #5 $8.32   9.865%   $9.1408   $9.14   $9.15   $9.10  
  Purchase #6 $192.78   9.688%   $211.4565   $211.46   $211.45   $211.50  
  Purchase #7 $182.34   7.465%   $195.9517   $195.95   $195.95   $196.00  
  7 purchase totals = $627.63       $675.5018   $675.50   $675.50   $675.50