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	$46.85	3.532%	$48.5047	$48.50	$48.50	$48.50
Purchase #2	$131.29	13.444%	$148.9406	$148.94	$148.95	$148.90
Purchase #3	$175.28	9.499%	$191.9298	$191.93	$191.95	$191.90
Purchase #4	$175.64	3.497%	$181.7821	$181.78	$181.80	$181.80
Purchase #5	$166.42	9.378%	$182.0269	$182.03	$182.05	$182.00
Purchase #6	$159.47	12.422%	$179.2794	$179.28	$179.30	$179.30
Purchase #7	$89.53	12.874%	$101.0561	$101.06	$101.05	$101.10
7 purchase totals =	$944.48		$1,033.5196	$1,033.52	$1,033.60	$1,033.50