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	$244.66	10.131%	$269.4465	$269.45	$269.45	$269.40
Purchase #2	$105.88	8.474%	$114.8523	$114.85	$114.85	$114.90
Purchase #3	$80.32	7.404%	$86.2669	$86.27	$86.25	$86.30
Purchase #4	$237.86	10.625%	$263.1326	$263.13	$263.15	$263.10
Purchase #5	$94.95	7.286%	$101.8681	$101.87	$101.85	$101.90
Purchase #6	$114.94	11.105%	$127.7041	$127.70	$127.70	$127.70
Purchase #7	$192.67	12.832%	$217.3934	$217.39	$217.40	$217.40
7 purchase totals =	$1,071.28		$1,180.6639	$1,180.66	$1,180.65	$1,180.70