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	$174.36	6.409%	$185.5347	$185.53	$185.55	$185.50
Purchase #2	$166.60	7.812%	$179.6148	$179.61	$179.60	$179.60
Purchase #3	$214.72	11.105%	$238.5647	$238.56	$238.55	$238.60
Purchase #4	$183.80	13.784%	$209.135	$209.14	$209.15	$209.10
Purchase #5	$163.53	5.189%	$172.0156	$172.02	$172.00	$172.00
Purchase #6	$156.77	10.102%	$172.6069	$172.61	$172.60	$172.60
Purchase #7	$55.64	8.641%	$60.4479	$60.45	$60.45	$60.40
7 purchase totals =	$1,115.42		$1,217.9196	$1,217.92	$1,217.90	$1,217.80