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	$49.94	13.589%	$56.7263	$56.73	$56.75	$56.70
Purchase #2	$81.37	11.367%	$90.6193	$90.62	$90.60	$90.60
Purchase #3	$101.94	3.496%	$105.5038	$105.50	$105.50	$105.50
Purchase #4	$152.34	13.672%	$173.1679	$173.17	$173.15	$173.20
Purchase #5	$208.91	10.701%	$231.2655	$231.27	$231.25	$231.30
Purchase #6	$70.65	12.437%	$79.4367	$79.44	$79.45	$79.40
Purchase #7	$167.72	4.237%	$174.8263	$174.83	$174.85	$174.80
7 purchase totals =	$832.87		$911.5458	$911.56	$911.55	$911.50