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	$40.50	7.723%	$43.6278	$43.63	$43.65	$43.60
Purchase #2	$173.65	8.735%	$188.8183	$188.82	$188.80	$188.80
Purchase #3	$245.50	13.693%	$279.1163	$279.12	$279.10	$279.10
Purchase #4	$128.50	10.638%	$142.1698	$142.17	$142.15	$142.20
Purchase #5	$151.96	8.776%	$165.296	$165.30	$165.30	$165.30
Purchase #6	$92.71	13.556%	$105.2778	$105.28	$105.30	$105.30
Purchase #7	$35.77	11.129%	$39.7508	$39.75	$39.75	$39.80
7 purchase totals =	$868.59		$964.0568	$964.07	$964.05	$964.10