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	$211.83	8.314%	$229.4415	$229.44	$229.45	$229.40
Purchase #2	$154.47	12.525%	$173.8174	$173.82	$173.80	$173.80
Purchase #3	$124.65	13.804%	$141.8567	$141.86	$141.85	$141.90
Purchase #4	$145.46	12.859%	$164.1647	$164.16	$164.15	$164.20
Purchase #5	$144.42	13.837%	$164.4034	$164.40	$164.40	$164.40
Purchase #6	$231.58	12.194%	$259.8189	$259.82	$259.80	$259.80
Purchase #7	$66.56	8.588%	$72.2762	$72.28	$72.30	$72.30
7 purchase totals =	$1,078.97		$1,205.7788	$1,205.78	$1,205.75	$1,205.80