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	$148.87	11.749%	$166.3607	$166.36	$166.35	$166.40
Purchase #2	$48.34	6.773%	$51.6141	$51.61	$51.60	$51.60
Purchase #3	$46.47	9.257%	$50.7717	$50.77	$50.75	$50.80
Purchase #4	$77.65	10.548%	$85.8405	$85.84	$85.85	$85.80
Purchase #5	$53.32	10.326%	$58.8258	$58.83	$58.85	$58.80
Purchase #6	$63.91	11.291%	$71.1261	$71.13	$71.15	$71.10
Purchase #7	$38.59	10.784%	$42.7515	$42.75	$42.75	$42.80
7 purchase totals =	$477.15		$527.2904	$527.29	$527.30	$527.30