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	$230.88	3.130%	$238.1065	$238.11	$238.10	$238.10
Purchase #2	$223.70	5.282%	$235.5158	$235.52	$235.50	$235.50
Purchase #3	$57.77	5.613%	$61.0126	$61.01	$61.00	$61.00
Purchase #4	$183.77	4.821%	$192.6296	$192.63	$192.65	$192.60
Purchase #5	$53.45	11.481%	$59.5866	$59.59	$59.60	$59.60
Purchase #6	$203.26	6.861%	$217.2057	$217.21	$217.20	$217.20
Purchase #7	$40.60	11.160%	$45.131	$45.13	$45.15	$45.10
7 purchase totals =	$993.43		$1,049.1878	$1,049.20	$1,049.20	$1,049.10