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	$101.83	9.609%	$111.6148	$111.61	$111.60	$111.60
Purchase #2	$166.34	3.769%	$172.6094	$172.61	$172.60	$172.60
Purchase #3	$10.55	12.419%	$11.8602	$11.86	$11.85	$11.90
Purchase #4	$180.67	4.253%	$188.3539	$188.35	$188.35	$188.40
Purchase #5	$149.73	11.287%	$166.63	$166.63	$166.65	$166.60
Purchase #6	$166.47	9.348%	$182.0316	$182.03	$182.05	$182.00
Purchase #7	$223.64	3.194%	$230.7831	$230.78	$230.80	$230.80
7 purchase totals =	$999.23		$1,063.8830	$1,063.87	$1,063.90	$1,063.90