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	$149.80	9.551%	$164.1074	$164.11	$164.10	$164.10
Purchase #2	$40.53	13.806%	$46.1256	$46.13	$46.15	$46.10
Purchase #3	$134.45	10.443%	$148.4906	$148.49	$148.50	$148.50
Purchase #4	$154.54	6.366%	$164.378	$164.38	$164.40	$164.40
Purchase #5	$149.39	11.396%	$166.4145	$166.41	$166.40	$166.40
Purchase #6	$48.27	13.382%	$54.7295	$54.73	$54.75	$54.70
Purchase #7	$217.28	10.593%	$240.2965	$240.30	$240.30	$240.30
7 purchase totals =	$894.26		$984.5421	$984.55	$984.60	$984.50