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	$228.72	11.191%	$254.3161	$254.32	$254.30	$254.30
Purchase #2	$14.61	6.475%	$15.556	$15.56	$15.55	$15.60
Purchase #3	$148.28	5.314%	$156.1596	$156.16	$156.15	$156.20
Purchase #4	$66.57	6.771%	$71.0775	$71.08	$71.10	$71.10
Purchase #5	$146.27	13.542%	$166.0779	$166.08	$166.10	$166.10
Purchase #6	$89.61	3.419%	$92.6738	$92.67	$92.65	$92.70
Purchase #7	$127.80	9.118%	$139.4528	$139.45	$139.45	$139.50
7 purchase totals =	$821.86		$895.3137	$895.32	$895.30	$895.50