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	$94.85	6.417%	$100.9365	$100.94	$100.95	$100.90
Purchase #2	$62.42	13.463%	$70.8236	$70.82	$70.80	$70.80
Purchase #3	$180.87	12.454%	$203.3955	$203.40	$203.40	$203.40
Purchase #4	$206.53	3.749%	$214.2728	$214.27	$214.25	$214.30
Purchase #5	$57.71	4.544%	$60.3323	$60.33	$60.35	$60.30
Purchase #6	$95.26	5.784%	$100.7698	$100.77	$100.75	$100.80
Purchase #7	$49.52	4.172%	$51.586	$51.59	$51.60	$51.60
7 purchase totals =	$747.16		$802.1165	$802.12	$802.10	$802.10