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	$10.51	5.621%	$11.1008	$11.10	$11.10	$11.10
Purchase #2	$72.64	6.869%	$77.6296	$77.63	$77.65	$77.60
Purchase #3	$146.41	3.462%	$151.4787	$151.48	$151.50	$151.50
Purchase #4	$172.42	10.231%	$190.0603	$190.06	$190.05	$190.10
Purchase #5	$22.33	8.862%	$24.3089	$24.31	$24.30	$24.30
Purchase #6	$74.41	11.482%	$82.9538	$82.95	$82.95	$83.00
Purchase #7	$92.74	7.212%	$99.4284	$99.43	$99.45	$99.40
7 purchase totals =	$591.46		$636.9605	$636.96	$637.00	$637.00