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	$61.52	6.665%	$65.6203	$65.62	$65.60	$65.60
Purchase #2	$222.72	11.826%	$249.0589	$249.06	$249.05	$249.10
Purchase #3	$216.41	5.507%	$228.3277	$228.33	$228.35	$228.30
Purchase #4	$158.79	10.362%	$175.2438	$175.24	$175.25	$175.20
Purchase #5	$146.80	5.556%	$154.9562	$154.96	$154.95	$155.00
Purchase #6	$250.95	13.630%	$285.1545	$285.15	$285.15	$285.20
Purchase #7	$173.64	13.339%	$196.8018	$196.80	$196.80	$196.80
7 purchase totals =	$1,230.83		$1,355.1632	$1,355.16	$1,355.15	$1,355.20