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	$186.70	12.182%	$209.4438	$209.44	$209.45	$209.40
Purchase #2	$95.89	9.767%	$105.2556	$105.26	$105.25	$105.30
Purchase #3	$144.65	5.605%	$152.7576	$152.76	$152.75	$152.80
Purchase #4	$117.32	5.269%	$123.5016	$123.50	$123.50	$123.50
Purchase #5	$72.69	9.278%	$79.4342	$79.43	$79.45	$79.40
Purchase #6	$193.65	8.624%	$210.3504	$210.35	$210.35	$210.40
Purchase #7	$229.82	11.356%	$255.9184	$255.92	$255.90	$255.90
7 purchase totals =	$1,040.72		$1,136.6616	$1,136.66	$1,136.65	$1,136.70