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	$159.81	4.406%	$166.8512	$166.85	$166.85	$166.90
Purchase #2	$160.83	5.783%	$170.1308	$170.13	$170.15	$170.10
Purchase #3	$97.63	3.397%	$100.9465	$100.95	$100.95	$100.90
Purchase #4	$244.86	9.729%	$268.6824	$268.68	$268.70	$268.70
Purchase #5	$47.78	12.280%	$53.6474	$53.65	$53.65	$53.60
Purchase #6	$138.93	9.606%	$152.2756	$152.28	$152.30	$152.30
Purchase #7	$98.53	8.427%	$106.8331	$106.83	$106.85	$106.80
7 purchase totals =	$948.37		$1,019.3670	$1,019.37	$1,019.45	$1,019.30