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	$185.78	5.833%	$196.6165	$196.62	$196.60	$196.60
Purchase #2	$60.68	6.627%	$64.7013	$64.70	$64.70	$64.70
Purchase #3	$66.85	5.117%	$70.2707	$70.27	$70.25	$70.30
Purchase #4	$149.72	10.840%	$165.9496	$165.95	$165.95	$165.90
Purchase #5	$42.46	11.368%	$47.2869	$47.29	$47.30	$47.30
Purchase #6	$177.45	4.212%	$184.9242	$184.92	$184.90	$184.90
Purchase #7	$103.80	10.768%	$114.9772	$114.98	$115.00	$115.00
7 purchase totals =	$786.74		$844.7264	$844.73	$844.70	$844.70