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	$157.89	9.262%	$172.5138	$172.51	$172.50	$172.50
Purchase #2	$183.56	9.116%	$200.2933	$200.29	$200.30	$200.30
Purchase #3	$234.65	3.791%	$243.5456	$243.55	$243.55	$243.50
Purchase #4	$16.34	13.709%	$18.5801	$18.58	$18.60	$18.60
Purchase #5	$15.50	13.277%	$17.5579	$17.56	$17.55	$17.60
Purchase #6	$195.58	11.233%	$217.5495	$217.55	$217.55	$217.50
Purchase #7	$241.73	5.519%	$255.0711	$255.07	$255.05	$255.10
7 purchase totals =	$1,045.25		$1,125.1113	$1,125.11	$1,125.10	$1,125.10