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	$178.78	5.332%	$188.3125	$188.31	$188.30	$188.30
Purchase #2	$21.71	13.202%	$24.5762	$24.58	$24.60	$24.60
Purchase #3	$107.32	4.443%	$112.0882	$112.09	$112.10	$112.10
Purchase #4	$141.84	4.536%	$148.2739	$148.27	$148.25	$148.30
Purchase #5	$190.96	11.677%	$213.2584	$213.26	$213.25	$213.30
Purchase #6	$241.89	9.164%	$264.0568	$264.06	$264.05	$264.10
Purchase #7	$226.73	3.581%	$234.8492	$234.85	$234.85	$234.80
7 purchase totals =	$1,109.23		$1,185.4152	$1,185.42	$1,185.40	$1,185.50