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	$166.34	11.593%	$185.6238	$185.62	$185.60	$185.60
Purchase #2	$206.89	12.724%	$233.2147	$233.21	$233.20	$233.20
Purchase #3	$250.46	3.160%	$258.3745	$258.37	$258.35	$258.40
Purchase #4	$203.75	10.846%	$225.8487	$225.85	$225.85	$225.80
Purchase #5	$143.87	3.592%	$149.0378	$149.04	$149.05	$149.00
Purchase #6	$243.84	7.626%	$262.4352	$262.44	$262.45	$262.40
Purchase #7	$103.36	7.475%	$111.0862	$111.09	$111.10	$111.10
7 purchase totals =	$1,318.51		$1,425.6209	$1,425.62	$1,425.60	$1,425.50