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	$187.37	13.441%	$212.5544	$212.55	$212.55	$212.60
Purchase #2	$111.69	13.558%	$126.8329	$126.83	$126.85	$126.80
Purchase #3	$141.77	13.329%	$160.6665	$160.67	$160.65	$160.70
Purchase #4	$128.57	4.574%	$134.4508	$134.45	$134.45	$134.50
Purchase #5	$229.56	5.549%	$242.2983	$242.30	$242.30	$242.30
Purchase #6	$89.69	3.404%	$92.743	$92.74	$92.75	$92.70
Purchase #7	$129.87	4.750%	$136.0388	$136.04	$136.05	$136.00
7 purchase totals =	$1,018.52		$1,105.5847	$1,105.58	$1,105.60	$1,105.60