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	$133.33	9.707%	$146.2723	$146.27	$146.25	$146.30
Purchase #2	$107.43	12.771%	$121.1499	$121.15	$121.15	$121.10
Purchase #3	$238.35	4.256%	$248.4942	$248.49	$248.50	$248.50
Purchase #4	$231.85	8.460%	$251.4645	$251.46	$251.45	$251.50
Purchase #5	$59.27	6.851%	$63.3306	$63.33	$63.35	$63.30
Purchase #6	$122.91	10.840%	$136.2334	$136.23	$136.25	$136.20
Purchase #7	$86.56	9.156%	$94.4854	$94.49	$94.50	$94.50
7 purchase totals =	$979.70		$1,061.4303	$1,061.42	$1,061.45	$1,061.40