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	$126.46	4.403%	$132.028	$132.03	$132.05	$132.00
Purchase #2	$144.30	10.680%	$159.7112	$159.71	$159.70	$159.70
Purchase #3	$38.65	5.680%	$40.8453	$40.85	$40.85	$40.80
Purchase #4	$148.63	6.392%	$158.1304	$158.13	$158.15	$158.10
Purchase #5	$61.30	12.338%	$68.8632	$68.86	$68.85	$68.90
Purchase #6	$103.50	11.224%	$115.1168	$115.12	$115.10	$115.10
Purchase #7	$60.85	11.565%	$67.8873	$67.89	$67.90	$67.90
7 purchase totals =	$683.69		$742.5822	$742.59	$742.60	$742.50