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	$57.61	10.501%	$63.6596	$63.66	$63.65	$63.70
Purchase #2	$48.86	9.428%	$53.4665	$53.47	$53.45	$53.50
Purchase #3	$79.32	3.403%	$82.0193	$82.02	$82.00	$82.00
Purchase #4	$161.72	4.528%	$169.0427	$169.04	$169.05	$169.00
Purchase #5	$29.87	12.737%	$33.6745	$33.67	$33.65	$33.70
Purchase #6	$167.27	3.640%	$173.3586	$173.36	$173.35	$173.40
Purchase #7	$28.60	4.324%	$29.8367	$29.84	$29.85	$29.80
7 purchase totals =	$573.25		$605.0579	$605.06	$605.00	$605.10