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 $92.26   3.568%   $95.5518   $95.55   $95.55   $95.60  
  Purchase #2 $154.93   4.218%   $161.4649   $161.46   $161.45   $161.50  
  Purchase #3 $196.47   7.767%   $211.7298   $211.73   $211.75   $211.70  
  Purchase #4 $129.93   7.120%   $139.181   $139.18   $139.20   $139.20  
  Purchase #5 $81.47   6.718%   $86.9432   $86.94   $86.95   $86.90  
  Purchase #6 $10.33   4.826%   $10.8285   $10.83   $10.85   $10.80  
  Purchase #7 $157.37   11.348%   $175.2283   $175.23   $175.25   $175.20  
  7 purchase totals = $822.76       $880.9275   $880.92   $881.00   $880.90