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	$52.38	3.104%	$54.0059	$54.01	$54.00	$54.00
Purchase #2	$189.85	3.671%	$196.8194	$196.82	$196.80	$196.80
Purchase #3	$140.80	12.163%	$157.9255	$157.93	$157.95	$157.90
Purchase #4	$171.83	9.277%	$187.7707	$187.77	$187.75	$187.80
Purchase #5	$166.78	11.375%	$185.7512	$185.75	$185.75	$185.80
Purchase #6	$239.27	12.586%	$269.3845	$269.38	$269.40	$269.40
Purchase #7	$163.59	7.773%	$176.3059	$176.31	$176.30	$176.30
7 purchase totals =	$1,124.50		$1,227.9631	$1,227.97	$1,227.95	$1,228.00