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	$87.43	4.670%	$91.513	$91.51	$91.50	$91.50
Purchase #2	$119.78	11.704%	$133.7991	$133.80	$133.80	$133.80
Purchase #3	$126.53	10.505%	$139.822	$139.82	$139.80	$139.80
Purchase #4	$12.47	12.446%	$14.022	$14.02	$14.00	$14.00
Purchase #5	$233.79	13.802%	$266.0577	$266.06	$266.05	$266.10
Purchase #6	$155.70	7.362%	$167.1626	$167.16	$167.15	$167.20
Purchase #7	$248.58	10.177%	$273.878	$273.88	$273.90	$273.90
7 purchase totals =	$984.28		$1,086.2544	$1,086.25	$1,086.20	$1,086.30