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	$32.52	6.524%	$34.6416	$34.64	$34.65	$34.60
Purchase #2	$98.55	7.584%	$106.024	$106.02	$106.00	$106.00
Purchase #3	$142.38	4.310%	$148.5166	$148.52	$148.50	$148.50
Purchase #4	$19.26	12.638%	$21.6941	$21.69	$21.70	$21.70
Purchase #5	$48.61	10.577%	$53.7515	$53.75	$53.75	$53.80
Purchase #6	$78.72	5.191%	$82.8064	$82.81	$82.80	$82.80
Purchase #7	$160.64	6.357%	$170.8519	$170.85	$170.85	$170.90
7 purchase totals =	$580.68		$618.2861	$618.28	$618.25	$618.30