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	$145.67	7.615%	$156.7628	$156.76	$156.75	$156.80
Purchase #2	$219.45	9.114%	$239.4507	$239.45	$239.45	$239.50
Purchase #3	$166.65	13.149%	$188.5628	$188.56	$188.55	$188.60
Purchase #4	$113.71	9.518%	$124.5329	$124.53	$124.55	$124.50
Purchase #5	$106.71	4.149%	$111.1374	$111.14	$111.15	$111.10
Purchase #6	$103.80	10.780%	$114.9896	$114.99	$115.00	$115.00
Purchase #7	$157.42	8.214%	$170.3505	$170.35	$170.35	$170.40
7 purchase totals =	$1,013.41		$1,105.7867	$1,105.78	$1,105.80	$1,105.90