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	$199.38	8.156%	$215.6414	$215.64	$215.65	$215.60
Purchase #2	$56.29	9.868%	$61.8447	$61.84	$61.85	$61.80
Purchase #3	$57.28	4.352%	$59.7728	$59.77	$59.75	$59.80
Purchase #4	$189.75	6.194%	$201.5031	$201.50	$201.50	$201.50
Purchase #5	$170.40	4.533%	$178.1242	$178.12	$178.10	$178.10
Purchase #6	$177.39	4.615%	$185.5765	$185.58	$185.60	$185.60
Purchase #7	$248.76	5.500%	$262.4418	$262.44	$262.45	$262.40
7 purchase totals =	$1,099.25		$1,164.9045	$1,164.89	$1,164.90	$1,164.80