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	$82.60	8.237%	$89.4038	$89.40	$89.40	$89.40
Purchase #2	$159.83	5.791%	$169.0858	$169.09	$169.10	$169.10
Purchase #3	$130.98	13.366%	$148.4868	$148.49	$148.50	$148.50
Purchase #4	$141.55	5.475%	$149.2999	$149.30	$149.30	$149.30
Purchase #5	$44.54	13.204%	$50.4211	$50.42	$50.40	$50.40
Purchase #6	$11.75	7.294%	$12.607	$12.61	$12.60	$12.60
Purchase #7	$127.31	11.852%	$142.3988	$142.40	$142.40	$142.40
7 purchase totals =	$698.56		$761.7032	$761.71	$761.70	$761.70