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	$151.88	4.426%	$158.6022	$158.60	$158.60	$158.60
Purchase #2	$236.69	3.752%	$245.5706	$245.57	$245.55	$245.60
Purchase #3	$233.55	12.579%	$262.9283	$262.93	$262.95	$262.90
Purchase #4	$40.83	11.624%	$45.5761	$45.58	$45.60	$45.60
Purchase #5	$64.33	6.392%	$68.442	$68.44	$68.45	$68.40
Purchase #6	$54.71	4.156%	$56.9837	$56.98	$57.00	$57.00
Purchase #7	$104.28	4.650%	$109.129	$109.13	$109.15	$109.10
7 purchase totals =	$886.27		$947.2319	$947.23	$947.30	$947.20