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	$145.38	6.561%	$154.9184	$154.92	$154.90	$154.90
Purchase #2	$179.74	4.230%	$187.343	$187.34	$187.35	$187.30
Purchase #3	$206.33	13.205%	$233.5759	$233.58	$233.60	$233.60
Purchase #4	$73.52	11.577%	$82.0314	$82.03	$82.05	$82.00
Purchase #5	$127.53	9.611%	$139.7869	$139.79	$139.80	$139.80
Purchase #6	$53.89	4.202%	$56.1545	$56.15	$56.15	$56.20
Purchase #7	$173.68	11.862%	$194.2819	$194.28	$194.30	$194.30
7 purchase totals =	$960.07		$1,048.0920	$1,048.09	$1,048.15	$1,048.10