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	$68.47	9.343%	$74.8672	$74.87	$74.85	$74.90
Purchase #2	$16.60	11.613%	$18.5278	$18.53	$18.55	$18.50
Purchase #3	$166.30	4.237%	$173.3461	$173.35	$173.35	$173.30
Purchase #4	$78.52	4.496%	$82.0503	$82.05	$82.05	$82.10
Purchase #5	$26.50	4.638%	$27.7291	$27.73	$27.75	$27.70
Purchase #6	$195.78	7.821%	$211.092	$211.09	$211.10	$211.10
Purchase #7	$42.28	8.547%	$45.8937	$45.89	$45.90	$45.90
7 purchase totals =	$594.45		$633.5062	$633.51	$633.55	$633.50