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	$40.37	8.361%	$43.7453	$43.75	$43.75	$43.70
Purchase #2	$154.64	8.539%	$167.8447	$167.84	$167.85	$167.80
Purchase #3	$242.54	13.734%	$275.8504	$275.85	$275.85	$275.90
Purchase #4	$149.70	10.702%	$165.7209	$165.72	$165.70	$165.70
Purchase #5	$212.69	3.253%	$219.6088	$219.61	$219.60	$219.60
Purchase #6	$208.59	11.800%	$233.2036	$233.20	$233.20	$233.20
Purchase #7	$112.76	12.778%	$127.1685	$127.17	$127.15	$127.20
7 purchase totals =	$1,121.29		$1,233.1422	$1,233.14	$1,233.10	$1,233.10