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	$165.29	3.613%	$171.2619	$171.26	$171.25	$171.30
Purchase #2	$232.33	7.800%	$250.4517	$250.45	$250.45	$250.50
Purchase #3	$74.90	3.144%	$77.2549	$77.25	$77.25	$77.30
Purchase #4	$119.73	6.186%	$127.1365	$127.14	$127.15	$127.10
Purchase #5	$205.86	11.784%	$230.1185	$230.12	$230.10	$230.10
Purchase #6	$16.55	13.427%	$18.7722	$18.77	$18.75	$18.80
Purchase #7	$218.42	10.693%	$241.7757	$241.78	$241.80	$241.80
7 purchase totals =	$1,033.08		$1,116.7714	$1,116.77	$1,116.75	$1,116.90