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 $116.49   8.667%   $126.5862   $126.59   $126.60   $126.60  
  Purchase #2 $237.62   9.248%   $259.5951   $259.60   $259.60   $259.60  
  Purchase #3 $63.72   3.555%   $65.9852   $65.99   $66.00   $66.00  
  Purchase #4 $208.37   7.185%   $223.3414   $223.34   $223.35   $223.30  
  Purchase #5 $244.90   10.553%   $270.7443   $270.74   $270.75   $270.70  
  Purchase #6 $135.94   3.631%   $140.876   $140.88   $140.90   $140.90  
  Purchase #7 $74.27   3.493%   $76.8643   $76.86   $76.85   $76.90  
  7 purchase totals = $1,081.31       $1,163.9925   $1,164.00   $1,164.05   $1,164.00