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	$168.97	6.325%	$179.6574	$179.66	$179.65	$179.70
Purchase #2	$53.56	4.799%	$56.1303	$56.13	$56.15	$56.10
Purchase #3	$194.91	3.501%	$201.7338	$201.73	$201.75	$201.70
Purchase #4	$110.47	7.346%	$118.5851	$118.59	$118.60	$118.60
Purchase #5	$168.63	4.680%	$176.5219	$176.52	$176.50	$176.50
Purchase #6	$115.30	10.540%	$127.4526	$127.45	$127.45	$127.50
Purchase #7	$59.74	11.297%	$66.4888	$66.49	$66.50	$66.50
7 purchase totals =	$871.58		$926.5699	$926.57	$926.60	$926.60