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	$105.67	7.698%	$113.8045	$113.80	$113.80	$113.80
Purchase #2	$115.87	8.805%	$126.0724	$126.07	$126.05	$126.10
Purchase #3	$127.34	13.212%	$144.1642	$144.16	$144.15	$144.20
Purchase #4	$84.88	5.672%	$89.6944	$89.69	$89.70	$89.70
Purchase #5	$14.27	4.719%	$14.9434	$14.94	$14.95	$14.90
Purchase #6	$159.47	5.588%	$168.3812	$168.38	$168.40	$168.40
Purchase #7	$115.40	6.843%	$123.2968	$123.30	$123.30	$123.30
7 purchase totals =	$722.90		$780.3569	$780.34	$780.35	$780.40