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	$230.61	13.766%	$262.3558	$262.36	$262.35	$262.40
Purchase #2	$150.83	10.149%	$166.1377	$166.14	$166.15	$166.10
Purchase #3	$66.72	6.712%	$71.1982	$71.20	$71.20	$71.20
Purchase #4	$241.59	4.773%	$253.1211	$253.12	$253.10	$253.10
Purchase #5	$51.69	5.645%	$54.6079	$54.61	$54.60	$54.60
Purchase #6	$146.28	8.716%	$159.0298	$159.03	$159.05	$159.00
Purchase #7	$34.41	10.138%	$37.8985	$37.90	$37.90	$37.90
7 purchase totals =	$922.13		$1,004.3490	$1,004.36	$1,004.35	$1,004.30