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 $206.67   3.661%   $214.2362   $214.24   $214.25   $214.20  
  Purchase #2 $241.33   11.461%   $268.9888   $268.99   $269.00   $269.00  
  Purchase #3 $209.36   13.525%   $237.6759   $237.68   $237.70   $237.70  
  Purchase #4 $5.99   11.387%   $6.6721   $6.67   $6.65   $6.70  
  Purchase #5 $161.37   6.561%   $171.9575   $171.96   $171.95   $172.00  
  Purchase #6 $125.59   3.188%   $129.5938   $129.59   $129.60   $129.60  
  Purchase #7 $211.35   10.230%   $232.9711   $232.97   $232.95   $233.00  
  7 purchase totals = $1,161.66       $1,262.0954   $1,262.10   $1,262.10   $1,262.20