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	$247.82	6.275%	$263.3707	$263.37	$263.35	$263.40
Purchase #2	$29.64	8.436%	$32.1404	$32.14	$32.15	$32.10
Purchase #3	$142.89	6.267%	$151.8449	$151.84	$151.85	$151.80
Purchase #4	$237.94	7.287%	$255.2787	$255.28	$255.30	$255.30
Purchase #5	$112.73	9.614%	$123.5679	$123.57	$123.55	$123.60
Purchase #6	$132.57	4.536%	$138.5834	$138.58	$138.60	$138.60
Purchase #7	$194.77	8.347%	$211.0275	$211.03	$211.05	$211.00
7 purchase totals =	$1,098.36		$1,175.8135	$1,175.81	$1,175.85	$1,175.80