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	$149.65	6.681%	$159.6481	$159.65	$159.65	$159.60
Purchase #2	$239.43	7.208%	$256.6881	$256.69	$256.70	$256.70
Purchase #3	$37.33	13.335%	$42.308	$42.31	$42.30	$42.30
Purchase #4	$46.41	6.113%	$49.247	$49.25	$49.25	$49.20
Purchase #5	$84.86	6.563%	$90.4294	$90.43	$90.45	$90.40
Purchase #6	$69.77	10.689%	$77.2277	$77.23	$77.25	$77.20
Purchase #7	$100.41	5.668%	$106.1012	$106.10	$106.10	$106.10
7 purchase totals =	$727.86		$781.6495	$781.66	$781.70	$781.50