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	$95.89	3.260%	$99.016	$99.02	$99.00	$99.00
Purchase #2	$207.42	11.576%	$231.4309	$231.43	$231.45	$231.40
Purchase #3	$15.29	4.309%	$15.9488	$15.95	$15.95	$15.90
Purchase #4	$103.80	11.485%	$115.7214	$115.72	$115.70	$115.70
Purchase #5	$149.72	10.606%	$165.5993	$165.60	$165.60	$165.60
Purchase #6	$191.82	4.235%	$199.9436	$199.94	$199.95	$199.90
Purchase #7	$195.45	7.122%	$209.3699	$209.37	$209.35	$209.40
7 purchase totals =	$959.39		$1,037.0299	$1,037.03	$1,037.00	$1,036.90