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	$152.55	4.144%	$158.8717	$158.87	$158.85	$158.90
Purchase #2	$249.28	6.290%	$264.9597	$264.96	$264.95	$265.00
Purchase #3	$242.62	4.752%	$254.1493	$254.15	$254.15	$254.10
Purchase #4	$146.65	12.232%	$164.5882	$164.59	$164.60	$164.60
Purchase #5	$123.30	3.214%	$127.2629	$127.26	$127.25	$127.30
Purchase #6	$183.35	13.761%	$208.5808	$208.58	$208.60	$208.60
Purchase #7	$101.71	12.388%	$114.3098	$114.31	$114.30	$114.30
7 purchase totals =	$1,199.46		$1,292.7224	$1,292.72	$1,292.70	$1,292.80