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	$49.33	6.102%	$52.3401	$52.34	$52.35	$52.30
Purchase #2	$167.87	10.326%	$185.2043	$185.20	$185.20	$185.20
Purchase #3	$178.96	9.376%	$195.7393	$195.74	$195.75	$195.70
Purchase #4	$227.47	6.313%	$241.8302	$241.83	$241.85	$241.80
Purchase #5	$215.53	7.397%	$231.4728	$231.47	$231.45	$231.50
Purchase #6	$107.95	3.396%	$111.616	$111.62	$111.60	$111.60
Purchase #7	$114.35	4.444%	$119.4317	$119.43	$119.45	$119.40
7 purchase totals =	$1,061.46		$1,137.6344	$1,137.63	$1,137.65	$1,137.50