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	$112.89	3.138%	$116.4325	$116.43	$116.45	$116.40
Purchase #2	$58.45	4.837%	$61.2772	$61.28	$61.30	$61.30
Purchase #3	$133.26	11.300%	$148.3184	$148.32	$148.30	$148.30
Purchase #4	$20.84	5.321%	$21.9489	$21.95	$21.95	$21.90
Purchase #5	$156.76	8.343%	$169.8385	$169.84	$169.85	$169.80
Purchase #6	$238.90	9.707%	$262.09	$262.09	$262.10	$262.10
Purchase #7	$75.33	10.784%	$83.4536	$83.45	$83.45	$83.50
7 purchase totals =	$796.43		$863.3591	$863.36	$863.40	$863.30