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	$77.69	10.111%	$85.5452	$85.55	$85.55	$85.50
Purchase #2	$45.35	9.362%	$49.5957	$49.60	$49.60	$49.60
Purchase #3	$141.29	13.669%	$160.6029	$160.60	$160.60	$160.60
Purchase #4	$198.62	5.623%	$209.7884	$209.79	$209.80	$209.80
Purchase #5	$185.40	10.634%	$205.1154	$205.12	$205.10	$205.10
Purchase #6	$150.93	13.550%	$171.381	$171.38	$171.40	$171.40
Purchase #7	$111.28	6.425%	$118.4297	$118.43	$118.45	$118.40
7 purchase totals =	$910.56		$1,000.4583	$1,000.47	$1,000.50	$1,000.40