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	$138.29	11.441%	$154.1118	$154.11	$154.10	$154.10
Purchase #2	$59.38	5.871%	$62.8662	$62.87	$62.85	$62.90
Purchase #3	$40.83	10.240%	$45.011	$45.01	$45.00	$45.00
Purchase #4	$212.40	8.407%	$230.2565	$230.26	$230.25	$230.30
Purchase #5	$118.75	7.672%	$127.8605	$127.86	$127.85	$127.90
Purchase #6	$209.73	9.267%	$229.1657	$229.17	$229.15	$229.20
Purchase #7	$188.98	6.103%	$200.5134	$200.51	$200.50	$200.50
7 purchase totals =	$968.36		$1,049.7851	$1,049.79	$1,049.70	$1,049.90