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 $194.52   10.123%   $214.2113   $214.21   $214.20   $214.20  
  Purchase #2 $197.36   7.147%   $211.4653   $211.47   $211.45   $211.50  
  Purchase #3 $116.88   8.724%   $127.0766   $127.08   $127.10   $127.10  
  Purchase #4 $51.49   12.714%   $58.0364   $58.04   $58.05   $58.00  
  Purchase #5 $161.81   11.617%   $180.6075   $180.61   $180.60   $180.60  
  Purchase #6 $79.64   7.873%   $85.9101   $85.91   $85.90   $85.90  
  Purchase #7 $161.41   4.452%   $168.596   $168.60   $168.60   $168.60  
  7 purchase totals = $963.11       $1,045.9032   $1,045.92   $1,045.90   $1,045.90