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	$145.63	4.729%	$152.5168	$152.52	$152.50	$152.50
Purchase #2	$174.88	5.538%	$184.5649	$184.56	$184.55	$184.60
Purchase #3	$106.40	5.168%	$111.8988	$111.90	$111.90	$111.90
Purchase #4	$226.84	6.158%	$240.8088	$240.81	$240.80	$240.80
Purchase #5	$173.29	6.731%	$184.9541	$184.95	$184.95	$185.00
Purchase #6	$214.56	4.727%	$224.7023	$224.70	$224.70	$224.70
Purchase #7	$138.41	9.347%	$151.3472	$151.35	$151.35	$151.30
7 purchase totals =	$1,180.01		$1,250.7929	$1,250.79	$1,250.75	$1,250.80