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	$166.48	4.302%	$173.642	$173.64	$173.65	$173.60
Purchase #2	$174.97	6.129%	$185.6939	$185.69	$185.70	$185.70
Purchase #3	$67.81	4.454%	$70.8303	$70.83	$70.85	$70.80
Purchase #4	$91.37	11.398%	$101.7844	$101.78	$101.80	$101.80
Purchase #5	$246.65	12.558%	$277.6243	$277.62	$277.60	$277.60
Purchase #6	$12.66	8.667%	$13.7572	$13.76	$13.75	$13.80
Purchase #7	$230.40	3.502%	$238.4686	$238.47	$238.45	$238.50
7 purchase totals =	$990.34		$1,061.8007	$1,061.79	$1,061.80	$1,061.80