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	$170.45	11.559%	$190.1523	$190.15	$190.15	$190.20
Purchase #2	$226.99	6.728%	$242.2619	$242.26	$242.25	$242.30
Purchase #3	$34.36	12.325%	$38.5949	$38.59	$38.60	$38.60
Purchase #4	$130.73	4.714%	$136.8926	$136.89	$136.90	$136.90
Purchase #5	$148.39	11.427%	$165.3465	$165.35	$165.35	$165.30
Purchase #6	$58.77	13.427%	$66.661	$66.66	$66.65	$66.70
Purchase #7	$249.37	5.754%	$263.7187	$263.72	$263.70	$263.70
7 purchase totals =	$1,019.06		$1,103.6279	$1,103.62	$1,103.60	$1,103.70