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	$169.95	5.856%	$179.9023	$179.90	$179.90	$179.90
Purchase #2	$158.96	8.639%	$172.6926	$172.69	$172.70	$172.70
Purchase #3	$176.62	9.596%	$193.5685	$193.57	$193.55	$193.60
Purchase #4	$150.89	3.696%	$156.4669	$156.47	$156.45	$156.50
Purchase #5	$153.91	11.727%	$171.959	$171.96	$171.95	$172.00
Purchase #6	$224.53	11.399%	$250.1242	$250.12	$250.10	$250.10
Purchase #7	$11.29	11.256%	$12.5608	$12.56	$12.55	$12.60
7 purchase totals =	$1,046.15		$1,137.2743	$1,137.27	$1,137.20	$1,137.40