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	$157.82	4.845%	$165.4664	$165.47	$165.45	$165.50
Purchase #2	$230.59	8.829%	$250.9488	$250.95	$250.95	$250.90
Purchase #3	$132.25	3.772%	$137.2385	$137.24	$137.25	$137.20
Purchase #4	$124.68	5.559%	$131.611	$131.61	$131.60	$131.60
Purchase #5	$120.86	5.390%	$127.3744	$127.37	$127.35	$127.40
Purchase #6	$8.29	8.311%	$8.979	$8.98	$9.00	$9.00
Purchase #7	$205.74	9.318%	$224.9109	$224.91	$224.90	$224.90
7 purchase totals =	$980.23		$1,046.5290	$1,046.53	$1,046.50	$1,046.50