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	$192.37	12.568%	$216.5471	$216.55	$216.55	$216.50
Purchase #2	$166.50	4.762%	$174.4287	$174.43	$174.45	$174.40
Purchase #3	$126.50	10.793%	$140.1531	$140.15	$140.15	$140.20
Purchase #4	$220.87	7.115%	$236.5849	$236.58	$236.60	$236.60
Purchase #5	$104.77	13.643%	$119.0638	$119.06	$119.05	$119.10
Purchase #6	$151.52	5.146%	$159.3172	$159.32	$159.30	$159.30
Purchase #7	$172.37	7.573%	$185.4236	$185.42	$185.40	$185.40
7 purchase totals =	$1,134.90		$1,231.5184	$1,231.51	$1,231.50	$1,231.50