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 $86.45   7.166%   $92.645   $92.65   $92.65   $92.60  
  Purchase #2 $144.25   10.103%   $158.8236   $158.82   $158.80   $158.80  
  Purchase #3 $99.53   4.140%   $103.6505   $103.65   $103.65   $103.70  
  Purchase #4 $186.83   11.809%   $208.8928   $208.89   $208.90   $208.90  
  Purchase #5 $190.77   12.688%   $214.9749   $214.97   $214.95   $215.00  
  Purchase #6 $193.52   9.550%   $212.0012   $212.00   $212.00   $212.00  
  Purchase #7 $167.82   3.463%   $173.6316   $173.63   $173.65   $173.60  
  7 purchase totals = $1,069.17       $1,164.6196   $1,164.61   $1,164.60   $1,164.60