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	$208.80	4.775%	$218.7702	$218.77	$218.75	$218.80
Purchase #2	$168.91	6.354%	$179.6425	$179.64	$179.65	$179.60
Purchase #3	$103.99	10.106%	$114.4992	$114.50	$114.50	$114.50
Purchase #4	$37.61	11.778%	$42.0397	$42.04	$42.05	$42.00
Purchase #5	$114.40	10.650%	$126.5836	$126.58	$126.60	$126.60
Purchase #6	$50.63	11.700%	$56.5537	$56.55	$56.55	$56.60
Purchase #7	$241.94	11.242%	$269.1389	$269.14	$269.15	$269.10
7 purchase totals =	$926.28		$1,007.2278	$1,007.22	$1,007.25	$1,007.20