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 $194.89   5.601%   $205.8058   $205.81   $205.80   $205.80  
  Purchase #2 $214.83   11.480%   $239.4925   $239.49   $239.50   $239.50  
  Purchase #3 $247.64   12.830%   $279.4122   $279.41   $279.40   $279.40  
  Purchase #4 $82.85   10.765%   $91.7688   $91.77   $91.75   $91.80  
  Purchase #5 $34.78   5.145%   $36.5694   $36.57   $36.55   $36.60  
  Purchase #6 $159.38   10.444%   $176.0256   $176.03   $176.05   $176.00  
  Purchase #7 $218.28   7.163%   $233.9154   $233.92   $233.90   $233.90  
  7 purchase totals = $1,152.65       $1,262.9897   $1,263.00   $1,262.95   $1,263.00