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 $116.62   9.111%   $127.2452   $127.25   $127.25   $127.20  
  Purchase #2 $31.76   12.383%   $35.6928   $35.69   $35.70   $35.70  
  Purchase #3 $16.49   8.767%   $17.9357   $17.94   $17.95   $17.90  
  Purchase #4 $230.71   3.417%   $238.5934   $238.59   $238.60   $238.60  
  Purchase #5 $154.37   8.212%   $167.0469   $167.05   $167.05   $167.00  
  Purchase #6 $169.76   7.319%   $182.1847   $182.18   $182.20   $182.20  
  Purchase #7 $165.54   6.455%   $176.2256   $176.23   $176.25   $176.20  
  7 purchase totals = $885.25       $944.9243   $944.93   $945.00   $944.80