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	$10.82	6.459%	$11.5189	$11.52	$11.50	$11.50
Purchase #2	$52.54	7.218%	$56.3323	$56.33	$56.35	$56.30
Purchase #3	$158.52	7.130%	$169.8225	$169.82	$169.80	$169.80
Purchase #4	$24.26	11.743%	$27.1089	$27.11	$27.10	$27.10
Purchase #5	$212.43	7.599%	$228.5726	$228.57	$228.55	$228.60
Purchase #6	$51.37	4.857%	$53.865	$53.87	$53.85	$53.90
Purchase #7	$152.96	12.609%	$172.2467	$172.25	$172.25	$172.20
7 purchase totals =	$662.90		$719.4669	$719.47	$719.40	$719.40