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	$116.71	5.277%	$122.8688	$122.87	$122.85	$122.90
Purchase #2	$69.40	12.515%	$78.0854	$78.09	$78.10	$78.10
Purchase #3	$127.59	3.784%	$132.418	$132.42	$132.40	$132.40
Purchase #4	$156.66	11.233%	$174.2576	$174.26	$174.25	$174.30
Purchase #5	$75.97	8.789%	$82.647	$82.65	$82.65	$82.60
Purchase #6	$89.31	7.633%	$96.127	$96.13	$96.15	$96.10
Purchase #7	$18.92	5.463%	$19.9536	$19.95	$19.95	$20.00
7 purchase totals =	$654.56		$706.3574	$706.37	$706.35	$706.40