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	$127.40	11.132%	$141.5822	$141.58	$141.60	$141.60
Purchase #2	$160.54	7.274%	$172.2177	$172.22	$172.20	$172.20
Purchase #3	$146.80	4.258%	$153.0507	$153.05	$153.05	$153.10
Purchase #4	$117.67	8.286%	$127.4201	$127.42	$127.40	$127.40
Purchase #5	$78.39	6.696%	$83.639	$83.64	$83.65	$83.60
Purchase #6	$236.85	12.471%	$266.3876	$266.39	$266.40	$266.40
Purchase #7	$147.69	11.727%	$165.0096	$165.01	$165.00	$165.00
7 purchase totals =	$1,015.34		$1,109.3069	$1,109.31	$1,109.30	$1,109.30