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 $179.61   8.396%   $194.6901   $194.69   $194.70   $194.70  
  Purchase #2 $157.51   11.606%   $175.7906   $175.79   $175.80   $175.80  
  Purchase #3 $76.59   6.850%   $81.8364   $81.84   $81.85   $81.80  
  Purchase #4 $114.38   3.167%   $118.0024   $118.00   $118.00   $118.00  
  Purchase #5 $248.68   10.622%   $275.0948   $275.09   $275.10   $275.10  
  Purchase #6 $51.58   4.108%   $53.6989   $53.70   $53.70   $53.70  
  Purchase #7 $31.29   13.841%   $35.6208   $35.62   $35.60   $35.60  
  7 purchase totals = $859.64       $934.7340   $934.73   $934.75   $934.70