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 $163.36   8.153%   $176.6787   $176.68   $176.70   $176.70  
  Purchase #2 $13.98   3.178%   $14.4243   $14.42   $14.40   $14.40  
  Purchase #3 $157.70   3.353%   $162.9877   $162.99   $163.00   $163.00  
  Purchase #4 $216.82   3.585%   $224.593   $224.59   $224.60   $224.60  
  Purchase #5 $72.83   5.433%   $76.7869   $76.79   $76.80   $76.80  
  Purchase #6 $22.87   5.832%   $24.2038   $24.20   $24.20   $24.20  
  Purchase #7 $176.26   9.248%   $192.5605   $192.56   $192.55   $192.60  
  7 purchase totals = $823.82       $872.2349   $872.23   $872.25   $872.30