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	$93.65	7.660%	$100.8236	$100.82	$100.80	$100.80
Purchase #2	$48.95	3.326%	$50.5781	$50.58	$50.60	$50.60
Purchase #3	$101.89	4.484%	$106.4587	$106.46	$106.45	$106.50
Purchase #4	$157.55	9.790%	$172.9741	$172.97	$172.95	$173.00
Purchase #5	$42.84	4.330%	$44.695	$44.70	$44.70	$44.70
Purchase #6	$48.78	4.550%	$50.9995	$51.00	$51.00	$51.00
Purchase #7	$189.59	13.326%	$214.8548	$214.85	$214.85	$214.90
7 purchase totals =	$683.25		$741.3838	$741.38	$741.35	$741.50