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	$116.38	9.689%	$127.6561	$127.66	$127.65	$127.70
Purchase #2	$37.74	4.338%	$39.3772	$39.38	$39.40	$39.40
Purchase #3	$95.58	10.699%	$105.8061	$105.81	$105.80	$105.80
Purchase #4	$197.33	9.605%	$216.2835	$216.28	$216.30	$216.30
Purchase #5	$76.30	7.805%	$82.2552	$82.26	$82.25	$82.30
Purchase #6	$208.71	6.545%	$222.3701	$222.37	$222.35	$222.40
Purchase #7	$138.52	7.539%	$148.963	$148.96	$148.95	$149.00
7 purchase totals =	$870.56		$942.7112	$942.72	$942.70	$942.90