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	$47.65	12.823%	$53.7602	$53.76	$53.75	$53.80
Purchase #2	$240.85	7.254%	$258.3213	$258.32	$258.30	$258.30
Purchase #3	$114.92	7.850%	$123.9412	$123.94	$123.95	$123.90
Purchase #4	$122.60	8.160%	$132.6042	$132.60	$132.60	$132.60
Purchase #5	$67.71	12.378%	$76.0911	$76.09	$76.10	$76.10
Purchase #6	$166.54	13.162%	$188.46	$188.46	$188.45	$188.50
Purchase #7	$77.33	8.210%	$83.6788	$83.68	$83.70	$83.70
7 purchase totals =	$837.60		$916.8568	$916.85	$916.85	$916.90