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	$105.80	5.832%	$111.9703	$111.97	$111.95	$112.00
Purchase #2	$115.45	10.301%	$127.3425	$127.34	$127.35	$127.30
Purchase #3	$214.62	7.201%	$230.0748	$230.07	$230.05	$230.10
Purchase #4	$205.72	11.847%	$230.0916	$230.09	$230.10	$230.10
Purchase #5	$82.88	13.562%	$94.1202	$94.12	$94.10	$94.10
Purchase #6	$163.38	13.419%	$185.304	$185.30	$185.30	$185.30
Purchase #7	$93.98	6.848%	$100.4158	$100.42	$100.40	$100.40
7 purchase totals =	$981.83		$1,079.3192	$1,079.31	$1,079.25	$1,079.30