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 $32.98   11.407%   $36.742   $36.74   $36.75   $36.70  
  Purchase #2 $84.54   11.162%   $93.9764   $93.98   $94.00   $94.00  
  Purchase #3 $94.38   10.260%   $104.0634   $104.06   $104.05   $104.10  
  Purchase #4 $142.58   7.248%   $152.9142   $152.91   $152.90   $152.90  
  Purchase #5 $84.36   10.184%   $92.9512   $92.95   $92.95   $93.00  
  Purchase #6 $197.82   6.459%   $210.5972   $210.60   $210.60   $210.60  
  Purchase #7 $191.42   12.704%   $215.738   $215.74   $215.75   $215.70  
  7 purchase totals = $828.08       $906.9824   $906.98   $907.00   $907.00