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 $206.81   3.582%   $214.2179   $214.22   $214.20   $214.20  
  Purchase #2 $24.83   7.491%   $26.69   $26.69   $26.70   $26.70  
  Purchase #3 $6.77   6.342%   $7.1994   $7.20   $7.20   $7.20  
  Purchase #4 $173.51   11.173%   $192.8963   $192.90   $192.90   $192.90  
  Purchase #5 $232.98   5.465%   $245.7124   $245.71   $245.70   $245.70  
  Purchase #6 $216.58   10.776%   $239.9187   $239.92   $239.90   $239.90  
  Purchase #7 $194.38   12.545%   $218.765   $218.77   $218.75   $218.80  
  7 purchase totals = $1,055.86       $1,145.3997   $1,145.41   $1,145.35   $1,145.40