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	$115.95	6.514%	$123.503	$123.50	$123.50	$123.50
Purchase #2	$148.64	7.577%	$159.9025	$159.90	$159.90	$159.90
Purchase #3	$167.25	10.861%	$185.415	$185.42	$185.40	$185.40
Purchase #4	$239.65	5.639%	$253.1639	$253.16	$253.15	$253.20
Purchase #5	$151.91	5.601%	$160.4185	$160.42	$160.40	$160.40
Purchase #6	$153.43	13.117%	$173.5554	$173.56	$173.55	$173.60
Purchase #7	$26.98	6.164%	$28.643	$28.64	$28.65	$28.60
7 purchase totals =	$1,003.81		$1,084.6013	$1,084.60	$1,084.55	$1,084.60