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	$241.72	4.102%	$251.6354	$251.64	$251.65	$251.60
Purchase #2	$132.26	10.348%	$145.9463	$145.95	$145.95	$145.90
Purchase #3	$173.87	7.242%	$186.4617	$186.46	$186.45	$186.50
Purchase #4	$174.99	3.251%	$180.6789	$180.68	$180.70	$180.70
Purchase #5	$29.79	12.351%	$33.4694	$33.47	$33.45	$33.50
Purchase #6	$112.72	13.852%	$128.334	$128.33	$128.35	$128.30
Purchase #7	$85.41	4.754%	$89.4704	$89.47	$89.45	$89.50
7 purchase totals =	$950.76		$1,015.9961	$1,016.00	$1,016.00	$1,016.00