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	$194.52	12.704%	$219.2318	$219.23	$219.25	$219.20
Purchase #2	$39.77	13.608%	$45.1819	$45.18	$45.20	$45.20
Purchase #3	$179.94	11.398%	$200.4496	$200.45	$200.45	$200.40
Purchase #4	$134.64	8.185%	$145.6603	$145.66	$145.65	$145.70
Purchase #5	$41.40	12.156%	$46.4326	$46.43	$46.45	$46.40
Purchase #6	$13.95	4.609%	$14.593	$14.59	$14.60	$14.60
Purchase #7	$229.69	6.606%	$244.8633	$244.86	$244.85	$244.90
7 purchase totals =	$833.91		$916.4125	$916.40	$916.45	$916.40