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	$191.52	12.853%	$216.1361	$216.14	$216.15	$216.10
Purchase #2	$49.54	11.131%	$55.0543	$55.05	$55.05	$55.10
Purchase #3	$12.94	6.606%	$13.7948	$13.79	$13.80	$13.80
Purchase #4	$148.83	3.360%	$153.8307	$153.83	$153.85	$153.80
Purchase #5	$199.53	5.831%	$211.1646	$211.16	$211.15	$211.20
Purchase #6	$118.29	7.726%	$127.4291	$127.43	$127.45	$127.40
Purchase #7	$149.30	7.672%	$160.7543	$160.75	$160.75	$160.80
7 purchase totals =	$869.95		$938.1639	$938.15	$938.20	$938.20