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	$113.81	12.222%	$127.7199	$127.72	$127.70	$127.70
Purchase #2	$18.31	12.319%	$20.5656	$20.57	$20.55	$20.60
Purchase #3	$23.84	13.825%	$27.1359	$27.14	$27.15	$27.10
Purchase #4	$85.43	8.167%	$92.4071	$92.41	$92.40	$92.40
Purchase #5	$198.94	7.672%	$214.2027	$214.20	$214.20	$214.20
Purchase #6	$247.55	12.530%	$278.568	$278.57	$278.55	$278.60
Purchase #7	$244.95	5.575%	$258.606	$258.61	$258.60	$258.60
7 purchase totals =	$932.83		$1,019.2052	$1,019.22	$1,019.15	$1,019.20