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	$118.90	6.463%	$126.5845	$126.58	$126.60	$126.60
Purchase #2	$133.99	13.414%	$151.9634	$151.96	$151.95	$152.00
Purchase #3	$46.85	13.348%	$53.1035	$53.10	$53.10	$53.10
Purchase #4	$21.39	6.810%	$22.8467	$22.85	$22.85	$22.80
Purchase #5	$245.89	13.811%	$279.8499	$279.85	$279.85	$279.80
Purchase #6	$85.31	4.520%	$89.166	$89.17	$89.15	$89.20
Purchase #7	$178.90	3.230%	$184.6785	$184.68	$184.70	$184.70
7 purchase totals =	$831.23		$908.1925	$908.19	$908.20	$908.20