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	$87.32	3.628%	$90.488	$90.49	$90.50	$90.50
Purchase #2	$45.33	7.225%	$48.6051	$48.61	$48.60	$48.60
Purchase #3	$190.45	10.635%	$210.7044	$210.70	$210.70	$210.70
Purchase #4	$214.91	9.203%	$234.6882	$234.69	$234.70	$234.70
Purchase #5	$68.75	5.451%	$72.4976	$72.50	$72.50	$72.50
Purchase #6	$177.77	3.858%	$184.6284	$184.63	$184.65	$184.60
Purchase #7	$62.77	4.728%	$65.7378	$65.74	$65.75	$65.70
7 purchase totals =	$847.30		$907.3495	$907.36	$907.40	$907.30