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 $67.48   8.567%   $73.261   $73.26   $73.25   $73.30  
  Purchase #2 $194.68   3.549%   $201.5892   $201.59   $201.60   $201.60  
  Purchase #3 $53.39   3.867%   $55.4546   $55.45   $55.45   $55.50  
  Purchase #4 $167.68   10.556%   $185.3803   $185.38   $185.40   $185.40  
  Purchase #5 $239.51   13.735%   $272.4067   $272.41   $272.40   $272.40  
  Purchase #6 $167.77   7.554%   $180.4433   $180.44   $180.45   $180.40  
  Purchase #7 $23.65   13.463%   $26.834   $26.83   $26.85   $26.80  
  7 purchase totals = $914.16       $995.3691   $995.36   $995.40   $995.40