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	$144.30	7.860%	$155.642	$155.64	$155.65	$155.60
Purchase #2	$155.72	4.376%	$162.5343	$162.53	$162.55	$162.50
Purchase #3	$178.29	3.231%	$184.0505	$184.05	$184.05	$184.10
Purchase #4	$188.95	5.520%	$199.38	$199.38	$199.40	$199.40
Purchase #5	$138.30	5.791%	$146.309	$146.31	$146.30	$146.30
Purchase #6	$100.58	10.414%	$111.0544	$111.05	$111.05	$111.10
Purchase #7	$90.68	5.128%	$95.3301	$95.33	$95.35	$95.30
7 purchase totals =	$996.82		$1,054.3003	$1,054.29	$1,054.35	$1,054.30