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 $194.63   11.160%   $216.3507   $216.35   $216.35   $216.40  
  Purchase #2 $230.49   10.342%   $254.3273   $254.33   $254.35   $254.30  
  Purchase #3 $136.26   13.215%   $154.2668   $154.27   $154.25   $154.30  
  Purchase #4 $229.73   4.357%   $239.7393   $239.74   $239.75   $239.70  
  Purchase #5 $79.68   8.382%   $86.3588   $86.36   $86.35   $86.40  
  Purchase #6 $137.64   4.394%   $143.6879   $143.69   $143.70   $143.70  
  Purchase #7 $53.54   13.511%   $60.7738   $60.77   $60.75   $60.80  
  7 purchase totals = $1,061.97       $1,155.5046   $1,155.51   $1,155.50   $1,155.60