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 $94.52   12.102%   $105.9588   $105.96   $105.95   $106.00  
  Purchase #2 $206.66   6.479%   $220.0495   $220.05   $220.05   $220.00  
  Purchase #3 $57.39   11.211%   $63.824   $63.82   $63.80   $63.80  
  Purchase #4 $140.83   7.230%   $151.012   $151.01   $151.00   $151.00  
  Purchase #5 $240.76   7.863%   $259.691   $259.69   $259.70   $259.70  
  Purchase #6 $220.34   8.131%   $238.2558   $238.26   $238.25   $238.30  
  Purchase #7 $95.88   10.210%   $105.6693   $105.67   $105.65   $105.70  
  7 purchase totals = $1,056.38       $1,144.4604   $1,144.46   $1,144.40   $1,144.50