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	$50.28	8.671%	$54.6398	$54.64	$54.65	$54.60
Purchase #2	$39.89	5.640%	$42.1398	$42.14	$42.15	$42.10
Purchase #3	$59.89	10.847%	$66.3863	$66.39	$66.40	$66.40
Purchase #4	$229.89	10.780%	$254.6721	$254.67	$254.65	$254.70
Purchase #5	$115.81	6.347%	$123.1605	$123.16	$123.15	$123.20
Purchase #6	$162.29	9.174%	$177.1785	$177.18	$177.20	$177.20
Purchase #7	$13.33	3.154%	$13.7504	$13.75	$13.75	$13.80
7 purchase totals =	$671.38		$731.9274	$731.93	$731.95	$732.00