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 $208.55   3.452%   $215.7491   $215.75   $215.75   $215.70  
  Purchase #2 $181.37   6.222%   $192.6548   $192.65   $192.65   $192.70  
  Purchase #3 $183.86   4.555%   $192.2348   $192.23   $192.25   $192.20  
  Purchase #4 $93.96   13.579%   $106.7188   $106.72   $106.70   $106.70  
  Purchase #5 $232.42   11.734%   $259.6922   $259.69   $259.70   $259.70  
  Purchase #6 $14.34   12.343%   $16.11   $16.11   $16.10   $16.10  
  Purchase #7 $117.58   11.377%   $130.9571   $130.96   $130.95   $131.00  
  7 purchase totals = $1,032.08       $1,114.1168   $1,114.11   $1,114.10   $1,114.10