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	$101.73	12.642%	$114.5907	$114.59	$114.60	$114.60
Purchase #2	$115.46	12.827%	$130.2701	$130.27	$130.25	$130.30
Purchase #3	$71.75	6.518%	$76.4267	$76.43	$76.45	$76.40
Purchase #4	$117.95	7.820%	$127.1737	$127.17	$127.15	$127.20
Purchase #5	$108.80	7.161%	$116.5912	$116.59	$116.60	$116.60
Purchase #6	$70.51	9.103%	$76.9285	$76.93	$76.95	$76.90
Purchase #7	$216.28	12.622%	$243.5789	$243.58	$243.60	$243.60
7 purchase totals =	$802.48		$885.5598	$885.56	$885.60	$885.60