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	$190.33	3.252%	$196.5195	$196.52	$196.50	$196.50
Purchase #2	$129.64	3.758%	$134.5119	$134.51	$134.50	$134.50
Purchase #3	$29.80	3.210%	$30.7566	$30.76	$30.75	$30.80
Purchase #4	$248.96	11.613%	$277.8717	$277.87	$277.85	$277.90
Purchase #5	$119.78	3.476%	$123.9436	$123.94	$123.95	$123.90
Purchase #6	$62.43	9.411%	$68.3053	$68.31	$68.30	$68.30
Purchase #7	$202.94	10.117%	$223.4714	$223.47	$223.45	$223.50
7 purchase totals =	$983.88		$1,055.3800	$1,055.38	$1,055.30	$1,055.40