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	$59.60	13.826%	$67.8403	$67.84	$67.85	$67.80
Purchase #2	$188.85	4.592%	$197.522	$197.52	$197.50	$197.50
Purchase #3	$134.36	7.367%	$144.2583	$144.26	$144.25	$144.30
Purchase #4	$56.99	11.325%	$63.4441	$63.44	$63.45	$63.40
Purchase #5	$209.56	6.216%	$222.5862	$222.59	$222.60	$222.60
Purchase #6	$26.35	10.129%	$29.019	$29.02	$29.00	$29.00
Purchase #7	$81.27	10.817%	$90.061	$90.06	$90.05	$90.10
7 purchase totals =	$756.98		$814.7309	$814.73	$814.70	$814.70