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	$149.26	11.319%	$166.1547	$166.15	$166.15	$166.20
Purchase #2	$249.85	11.660%	$278.9825	$278.98	$279.00	$279.00
Purchase #3	$96.46	13.831%	$109.8014	$109.80	$109.80	$109.80
Purchase #4	$113.65	11.829%	$127.0937	$127.09	$127.10	$127.10
Purchase #5	$68.40	6.140%	$72.5998	$72.60	$72.60	$72.60
Purchase #6	$239.60	5.127%	$251.8843	$251.88	$251.90	$251.90
Purchase #7	$130.69	10.556%	$144.4856	$144.49	$144.50	$144.50
7 purchase totals =	$1,047.91		$1,151.0020	$1,150.99	$1,151.05	$1,151.10