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	$46.57	3.741%	$48.3122	$48.31	$48.30	$48.30
Purchase #2	$96.30	3.428%	$99.6012	$99.60	$99.60	$99.60
Purchase #3	$54.45	5.387%	$57.3832	$57.38	$57.40	$57.40
Purchase #4	$8.51	10.262%	$9.3833	$9.38	$9.40	$9.40
Purchase #5	$84.72	3.221%	$87.4488	$87.45	$87.45	$87.40
Purchase #6	$139.93	4.607%	$146.3766	$146.38	$146.40	$146.40
Purchase #7	$149.79	10.456%	$165.452	$165.45	$165.45	$165.50
7 purchase totals =	$580.27		$613.9573	$613.95	$614.00	$614.00