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	$159.69	12.570%	$179.763	$179.76	$179.75	$179.80
Purchase #2	$37.61	8.583%	$40.8381	$40.84	$40.85	$40.80
Purchase #3	$134.92	13.399%	$152.9979	$153.00	$153.00	$153.00
Purchase #4	$211.54	3.467%	$218.8741	$218.87	$218.85	$218.90
Purchase #5	$230.82	8.788%	$251.1045	$251.10	$251.10	$251.10
Purchase #6	$181.51	9.426%	$198.6191	$198.62	$198.60	$198.60
Purchase #7	$147.78	4.162%	$153.9306	$153.93	$153.95	$153.90
7 purchase totals =	$1,103.87		$1,196.1273	$1,196.12	$1,196.10	$1,196.10