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	$106.79	4.700%	$111.8091	$111.81	$111.80	$111.80
Purchase #2	$228.79	7.203%	$245.2697	$245.27	$245.25	$245.30
Purchase #3	$116.77	11.326%	$129.9954	$130.00	$130.00	$130.00
Purchase #4	$240.52	4.326%	$250.9249	$250.92	$250.90	$250.90
Purchase #5	$106.36	4.831%	$111.4983	$111.50	$111.50	$111.50
Purchase #6	$173.42	13.425%	$196.7016	$196.70	$196.70	$196.70
Purchase #7	$210.44	9.477%	$230.3834	$230.38	$230.40	$230.40
7 purchase totals =	$1,183.09		$1,276.5824	$1,276.58	$1,276.55	$1,276.60