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	$120.68	11.654%	$134.744	$134.74	$134.75	$134.70
Purchase #2	$117.27	9.813%	$128.7777	$128.78	$128.80	$128.80
Purchase #3	$98.40	13.420%	$111.6053	$111.61	$111.60	$111.60
Purchase #4	$131.56	6.452%	$140.0483	$140.05	$140.05	$140.00
Purchase #5	$162.29	6.272%	$172.4688	$172.47	$172.45	$172.50
Purchase #6	$7.40	7.161%	$7.9299	$7.93	$7.95	$7.90
Purchase #7	$28.42	4.336%	$29.6523	$29.65	$29.65	$29.70
7 purchase totals =	$666.02		$725.2263	$725.23	$725.25	$725.20