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	$108.87	12.188%	$122.1391	$122.14	$122.15	$122.10
Purchase #2	$49.99	13.400%	$56.6887	$56.69	$56.70	$56.70
Purchase #3	$46.72	5.486%	$49.2831	$49.28	$49.30	$49.30
Purchase #4	$161.94	3.334%	$167.3391	$167.34	$167.35	$167.30
Purchase #5	$100.46	10.821%	$111.3308	$111.33	$111.35	$111.30
Purchase #6	$76.43	9.440%	$83.645	$83.65	$83.65	$83.60
Purchase #7	$151.81	9.452%	$166.1591	$166.16	$166.15	$166.20
7 purchase totals =	$696.22		$756.5849	$756.59	$756.65	$756.50