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	$244.71	7.196%	$262.3193	$262.32	$262.30	$262.30
Purchase #2	$215.38	9.288%	$235.3845	$235.38	$235.40	$235.40
Purchase #3	$169.70	10.455%	$187.4421	$187.44	$187.45	$187.40
Purchase #4	$138.64	4.586%	$144.998	$145.00	$145.00	$145.00
Purchase #5	$158.33	13.565%	$179.8075	$179.81	$179.80	$179.80
Purchase #6	$135.98	11.620%	$151.7809	$151.78	$151.80	$151.80
Purchase #7	$68.54	5.145%	$72.0664	$72.07	$72.05	$72.10
7 purchase totals =	$1,131.28		$1,233.7987	$1,233.80	$1,233.80	$1,233.80