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 $57.76   7.847%   $62.2924   $62.29   $62.30   $62.30  
  Purchase #2 $158.98   8.295%   $172.1674   $172.17   $172.15   $172.20  
  Purchase #3 $29.49   3.219%   $30.4393   $30.44   $30.45   $30.40  
  Purchase #4 $178.78   7.828%   $192.7749   $192.77   $192.75   $192.80  
  Purchase #5 $126.43   7.157%   $135.4786   $135.48   $135.50   $135.50  
  Purchase #6 $206.39   11.437%   $229.9948   $229.99   $230.00   $230.00  
  Purchase #7 $221.25   4.140%   $230.4098   $230.41   $230.40   $230.40  
  7 purchase totals = $979.08       $1,053.5572   $1,053.55   $1,053.55   $1,053.60