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	$146.65	12.835%	$165.4725	$165.47	$165.45	$165.50
Purchase #2	$224.74	7.435%	$241.4494	$241.45	$241.45	$241.40
Purchase #3	$63.39	4.632%	$66.3262	$66.33	$66.35	$66.30
Purchase #4	$222.71	10.344%	$245.7471	$245.75	$245.75	$245.70
Purchase #5	$155.94	3.754%	$161.794	$161.79	$161.80	$161.80
Purchase #6	$9.49	13.510%	$10.7721	$10.77	$10.75	$10.80
Purchase #7	$179.25	3.233%	$185.0452	$185.05	$185.05	$185.00
7 purchase totals =	$1,002.17		$1,076.6065	$1,076.61	$1,076.60	$1,076.50