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	$82.82	3.401%	$85.6367	$85.64	$85.65	$85.60
Purchase #2	$216.53	7.824%	$233.4713	$233.47	$233.45	$233.50
Purchase #3	$29.74	7.693%	$32.0279	$32.03	$32.05	$32.00
Purchase #4	$139.49	13.484%	$158.2988	$158.30	$158.30	$158.30
Purchase #5	$61.84	6.438%	$65.8213	$65.82	$65.80	$65.80
Purchase #6	$38.75	6.538%	$41.2835	$41.28	$41.30	$41.30
Purchase #7	$107.35	7.683%	$115.5977	$115.60	$115.60	$115.60
7 purchase totals =	$676.52		$732.1372	$732.14	$732.15	$732.10