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	$215.63	3.189%	$222.5064	$222.51	$222.50	$222.50
Purchase #2	$71.59	9.446%	$78.3524	$78.35	$78.35	$78.40
Purchase #3	$222.65	3.138%	$229.6368	$229.64	$229.65	$229.60
Purchase #4	$111.25	6.597%	$118.5892	$118.59	$118.60	$118.60
Purchase #5	$74.56	12.580%	$83.9396	$83.94	$83.95	$83.90
Purchase #6	$250.66	6.626%	$267.2687	$267.27	$267.25	$267.30
Purchase #7	$144.80	4.728%	$151.6461	$151.65	$151.65	$151.60
7 purchase totals =	$1,091.14		$1,151.9392	$1,151.95	$1,151.95	$1,151.90