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	$111.80	7.200%	$119.8496	$119.85	$119.85	$119.80
Purchase #2	$36.71	6.409%	$39.0627	$39.06	$39.05	$39.10
Purchase #3	$155.34	13.124%	$175.7268	$175.73	$175.75	$175.70
Purchase #4	$241.54	6.232%	$256.5928	$256.59	$256.60	$256.60
Purchase #5	$169.61	5.627%	$179.154	$179.15	$179.15	$179.20
Purchase #6	$218.27	3.124%	$225.0888	$225.09	$225.10	$225.10
Purchase #7	$178.62	3.847%	$185.4915	$185.49	$185.50	$185.50
7 purchase totals =	$1,111.89		$1,180.9662	$1,180.96	$1,181.00	$1,181.00