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	$120.58	5.803%	$127.5773	$127.58	$127.60	$127.60
Purchase #2	$44.70	4.207%	$46.5805	$46.58	$46.60	$46.60
Purchase #3	$15.59	12.154%	$17.4848	$17.48	$17.50	$17.50
Purchase #4	$115.64	7.112%	$123.8643	$123.86	$123.85	$123.90
Purchase #5	$10.80	13.682%	$12.2777	$12.28	$12.30	$12.30
Purchase #6	$72.60	6.513%	$77.3284	$77.33	$77.35	$77.30
Purchase #7	$186.68	12.183%	$209.4232	$209.42	$209.40	$209.40
7 purchase totals =	$566.59		$614.5362	$614.53	$614.60	$614.60