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	$151.72	10.500%	$167.6506	$167.65	$167.65	$167.70
Purchase #2	$244.83	5.843%	$259.1354	$259.14	$259.15	$259.10
Purchase #3	$126.73	4.337%	$132.2263	$132.23	$132.25	$132.20
Purchase #4	$100.31	3.666%	$103.9874	$103.99	$104.00	$104.00
Purchase #5	$138.25	12.189%	$155.1013	$155.10	$155.10	$155.10
Purchase #6	$208.46	13.640%	$236.8939	$236.89	$236.90	$236.90
Purchase #7	$41.99	8.566%	$45.5869	$45.59	$45.60	$45.60
7 purchase totals =	$1,012.29		$1,100.5818	$1,100.59	$1,100.65	$1,100.60