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	$196.33	13.847%	$223.5158	$223.52	$223.50	$223.50
Purchase #2	$54.61	10.143%	$60.1491	$60.15	$60.15	$60.10
Purchase #3	$80.33	9.114%	$87.6513	$87.65	$87.65	$87.70
Purchase #4	$169.81	4.518%	$177.482	$177.48	$177.50	$177.50
Purchase #5	$151.63	4.354%	$158.232	$158.23	$158.25	$158.20
Purchase #6	$104.49	7.613%	$112.4448	$112.44	$112.45	$112.40
Purchase #7	$249.62	12.507%	$280.84	$280.84	$280.85	$280.80
7 purchase totals =	$1,006.82		$1,100.3150	$1,100.31	$1,100.35	$1,100.20