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	$85.45	5.835%	$90.436	$90.44	$90.45	$90.40
Purchase #2	$139.45	4.599%	$145.8633	$145.86	$145.85	$145.90
Purchase #3	$95.65	4.407%	$99.8653	$99.87	$99.85	$99.90
Purchase #4	$49.48	13.318%	$56.0697	$56.07	$56.05	$56.10
Purchase #5	$197.93	3.222%	$204.3073	$204.31	$204.30	$204.30
Purchase #6	$227.61	4.168%	$237.0968	$237.10	$237.10	$237.10
Purchase #7	$217.98	8.109%	$235.656	$235.66	$235.65	$235.70
7 purchase totals =	$1,013.55		$1,069.2944	$1,069.31	$1,069.25	$1,069.40