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	$66.87	9.404%	$73.1585	$73.16	$73.15	$73.20
Purchase #2	$156.65	10.383%	$172.915	$172.92	$172.90	$172.90
Purchase #3	$152.28	4.510%	$159.1478	$159.15	$159.15	$159.10
Purchase #4	$96.97	3.864%	$100.7169	$100.72	$100.70	$100.70
Purchase #5	$130.53	11.610%	$145.6845	$145.68	$145.70	$145.70
Purchase #6	$187.46	13.784%	$213.2995	$213.30	$213.30	$213.30
Purchase #7	$135.74	13.298%	$153.7907	$153.79	$153.80	$153.80
7 purchase totals =	$926.50		$1,018.7129	$1,018.72	$1,018.70	$1,018.70