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 $180.47   8.430%   $195.6836   $195.68   $195.70   $195.70  
  Purchase #2 $111.88   11.510%   $124.7574   $124.76   $124.75   $124.80  
  Purchase #3 $23.60   6.123%   $25.045   $25.05   $25.05   $25.00  
  Purchase #4 $104.40   8.246%   $113.0088   $113.01   $113.00   $113.00  
  Purchase #5 $63.98   12.526%   $71.9941   $71.99   $72.00   $72.00  
  Purchase #6 $164.47   10.188%   $181.2262   $181.23   $181.25   $181.20  
  Purchase #7 $81.32   6.807%   $86.8555   $86.86   $86.85   $86.90  
  7 purchase totals = $730.12       $798.5706   $798.58   $798.60   $798.60