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	$212.50	13.572%	$241.3405	$241.34	$241.35	$241.30
Purchase #2	$171.69	5.345%	$180.8668	$180.87	$180.85	$180.90
Purchase #3	$172.31	7.810%	$185.7674	$185.77	$185.75	$185.80
Purchase #4	$132.73	8.475%	$143.9789	$143.98	$144.00	$144.00
Purchase #5	$249.46	3.210%	$257.4677	$257.47	$257.45	$257.50
Purchase #6	$231.47	4.191%	$241.1709	$241.17	$241.15	$241.20
Purchase #7	$61.69	3.474%	$63.8331	$63.83	$63.85	$63.80
7 purchase totals =	$1,231.85		$1,314.4253	$1,314.43	$1,314.40	$1,314.50