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	$211.83	9.431%	$231.8077	$231.81	$231.80	$231.80
Purchase #2	$208.51	6.825%	$222.7408	$222.74	$222.75	$222.70
Purchase #3	$108.27	4.401%	$113.035	$113.04	$113.05	$113.00
Purchase #4	$9.94	6.409%	$10.5771	$10.58	$10.60	$10.60
Purchase #5	$209.81	10.379%	$231.5862	$231.59	$231.60	$231.60
Purchase #6	$173.52	10.427%	$191.6129	$191.61	$191.60	$191.60
Purchase #7	$141.84	10.370%	$156.5488	$156.55	$156.55	$156.50
7 purchase totals =	$1,063.72		$1,157.9085	$1,157.92	$1,157.95	$1,157.80