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 $44.40   4.122%   $46.2302   $46.23   $46.25   $46.20  
  Purchase #2 $187.60   4.203%   $195.4848   $195.48   $195.50   $195.50  
  Purchase #3 $117.88   4.832%   $123.576   $123.58   $123.60   $123.60  
  Purchase #4 $218.53   7.874%   $235.7371   $235.74   $235.75   $235.70  
  Purchase #5 $230.58   10.136%   $253.9516   $253.95   $253.95   $254.00  
  Purchase #6 $52.31   3.104%   $53.9337   $53.93   $53.95   $53.90  
  Purchase #7 $6.67   11.574%   $7.442   $7.44   $7.45   $7.40  
  7 purchase totals = $857.97       $916.3554   $916.35   $916.45   $916.30