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	$211.72	10.328%	$233.5864	$233.59	$233.60	$233.60
Purchase #2	$204.47	10.152%	$225.2278	$225.23	$225.25	$225.20
Purchase #3	$139.67	5.298%	$147.0697	$147.07	$147.05	$147.10
Purchase #4	$53.34	7.325%	$57.2472	$57.25	$57.25	$57.20
Purchase #5	$125.80	12.219%	$141.1715	$141.17	$141.15	$141.20
Purchase #6	$10.93	7.240%	$11.7213	$11.72	$11.70	$11.70
Purchase #7	$164.85	12.182%	$184.932	$184.93	$184.95	$184.90
7 purchase totals =	$910.78		$1,000.9559	$1,000.96	$1,000.95	$1,000.90