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 $94.91   10.233%   $104.6221   $104.62   $104.60   $104.60  
  Purchase #2 $10.96   6.110%   $11.6297   $11.63   $11.65   $11.60  
  Purchase #3 $16.25   8.737%   $17.6698   $17.67   $17.65   $17.70  
  Purchase #4 $59.31   3.327%   $61.2832   $61.28   $61.30   $61.30  
  Purchase #5 $18.90   3.251%   $19.5144   $19.51   $19.50   $19.50  
  Purchase #6 $160.44   9.866%   $176.269   $176.27   $176.25   $176.30  
  Purchase #7 $72.60   4.726%   $76.0311   $76.03   $76.05   $76.00  
  7 purchase totals = $433.37       $467.0193   $467.01   $467.00   $467.00