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 $123.95   8.609%   $134.6209   $134.62   $134.60   $134.60  
  Purchase #2 $26.84   8.379%   $29.0889   $29.09   $29.10   $29.10  
  Purchase #3 $233.85   4.626%   $244.6679   $244.67   $244.65   $244.70  
  Purchase #4 $30.25   13.129%   $34.2215   $34.22   $34.20   $34.20  
  Purchase #5 $55.73   11.273%   $62.0124   $62.01   $62.00   $62.00  
  Purchase #6 $59.50   10.214%   $65.5773   $65.58   $65.60   $65.60  
  Purchase #7 $206.72   8.804%   $224.9196   $224.92   $224.90   $224.90  
  7 purchase totals = $736.84       $795.1085   $795.11   $795.05   $795.10