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	$142.36	11.278%	$158.4154	$158.42	$158.40	$158.40
Purchase #2	$95.82	5.487%	$101.0776	$101.08	$101.10	$101.10
Purchase #3	$43.90	4.574%	$45.908	$45.91	$45.90	$45.90
Purchase #4	$105.60	5.195%	$111.0859	$111.09	$111.10	$111.10
Purchase #5	$47.71	8.313%	$51.6761	$51.68	$51.70	$51.70
Purchase #6	$192.92	12.363%	$216.7707	$216.77	$216.75	$216.80
Purchase #7	$196.55	3.735%	$203.8911	$203.89	$203.90	$203.90
7 purchase totals =	$824.86		$888.8248	$888.84	$888.85	$888.90