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	$26.28	3.714%	$27.256	$27.26	$27.25	$27.30
Purchase #2	$229.66	5.633%	$242.5967	$242.60	$242.60	$242.60
Purchase #3	$142.35	11.829%	$159.1886	$159.19	$159.20	$159.20
Purchase #4	$50.83	4.527%	$53.1311	$53.13	$53.15	$53.10
Purchase #5	$168.68	10.169%	$185.8331	$185.83	$185.85	$185.80
Purchase #6	$111.39	6.414%	$118.5346	$118.53	$118.55	$118.50
Purchase #7	$207.77	9.506%	$227.5206	$227.52	$227.50	$227.50
7 purchase totals =	$936.96		$1,014.0607	$1,014.06	$1,014.10	$1,014.00