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 $68.31   8.251%   $73.9463   $73.95   $73.95   $73.90  
  Purchase #2 $164.57   6.307%   $174.9494   $174.95   $174.95   $174.90  
  Purchase #3 $34.70   6.141%   $36.8309   $36.83   $36.85   $36.80  
  Purchase #4 $69.41   4.401%   $72.4647   $72.46   $72.45   $72.50  
  Purchase #5 $213.54   8.483%   $231.6546   $231.65   $231.65   $231.70  
  Purchase #6 $61.54   10.454%   $67.9734   $67.97   $67.95   $68.00  
  Purchase #7 $220.40   10.737%   $244.0643   $244.06   $244.05   $244.10  
  7 purchase totals = $832.47       $901.8836   $901.87   $901.85   $901.90