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	$56.99	9.469%	$62.3864	$62.39	$62.40	$62.40
Purchase #2	$128.64	7.774%	$138.6405	$138.64	$138.65	$138.60
Purchase #3	$54.73	8.663%	$59.4713	$59.47	$59.45	$59.50
Purchase #4	$34.45	10.281%	$37.9918	$37.99	$38.00	$38.00
Purchase #5	$82.51	12.473%	$92.8015	$92.80	$92.80	$92.80
Purchase #6	$99.93	3.597%	$103.5245	$103.52	$103.50	$103.50
Purchase #7	$241.57	5.687%	$255.3081	$255.31	$255.30	$255.30
7 purchase totals =	$698.82		$750.1241	$750.12	$750.10	$750.10