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	$87.25	3.563%	$90.3587	$90.36	$90.35	$90.40
Purchase #2	$36.33	3.499%	$37.6012	$37.60	$37.60	$37.60
Purchase #3	$195.34	11.183%	$217.1849	$217.18	$217.20	$217.20
Purchase #4	$94.43	8.589%	$102.5406	$102.54	$102.55	$102.50
Purchase #5	$35.78	3.548%	$37.0495	$37.05	$37.05	$37.00
Purchase #6	$14.38	4.737%	$15.0612	$15.06	$15.05	$15.10
Purchase #7	$108.58	11.864%	$121.4619	$121.46	$121.45	$121.50
7 purchase totals =	$572.09		$621.2580	$621.25	$621.25	$621.30