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 $44.79   3.771%   $46.479   $46.48   $46.50   $46.50  
  Purchase #2 $192.35   12.497%   $216.388   $216.39   $216.40   $216.40  
  Purchase #3 $24.58   6.444%   $26.1639   $26.16   $26.15   $26.20  
  Purchase #4 $220.91   8.623%   $239.9591   $239.96   $239.95   $240.00  
  Purchase #5 $14.44   12.252%   $16.2092   $16.21   $16.20   $16.20  
  Purchase #6 $118.69   7.532%   $127.6297   $127.63   $127.65   $127.60  
  Purchase #7 $71.40   11.285%   $79.4575   $79.46   $79.45   $79.50  
  7 purchase totals = $687.16       $752.2864   $752.29   $752.30   $752.40