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	$156.65	5.701%	$165.5806	$165.58	$165.60	$165.60
Purchase #2	$41.85	9.804%	$45.953	$45.95	$45.95	$46.00
Purchase #3	$246.75	7.106%	$264.2841	$264.28	$264.30	$264.30
Purchase #4	$242.62	9.806%	$266.4113	$266.41	$266.40	$266.40
Purchase #5	$79.98	6.335%	$85.0467	$85.05	$85.05	$85.00
Purchase #6	$145.66	8.761%	$158.4213	$158.42	$158.40	$158.40
Purchase #7	$86.93	10.209%	$95.8047	$95.80	$95.80	$95.80
7 purchase totals =	$1,000.44		$1,081.5017	$1,081.49	$1,081.50	$1,081.50