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	$90.43	5.279%	$95.2038	$95.20	$95.20	$95.20
Purchase #2	$134.37	8.274%	$145.4878	$145.49	$145.50	$145.50
Purchase #3	$155.40	6.678%	$165.7776	$165.78	$165.80	$165.80
Purchase #4	$167.32	10.813%	$185.4123	$185.41	$185.40	$185.40
Purchase #5	$209.53	13.310%	$237.4184	$237.42	$237.40	$237.40
Purchase #6	$237.72	6.117%	$252.2613	$252.26	$252.25	$252.30
Purchase #7	$56.86	12.382%	$63.9004	$63.90	$63.90	$63.90
7 purchase totals =	$1,051.63		$1,145.4616	$1,145.46	$1,145.45	$1,145.50