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	$63.71	11.682%	$71.1526	$71.15	$71.15	$71.20
Purchase #2	$183.34	10.754%	$203.0564	$203.06	$203.05	$203.10
Purchase #3	$32.48	4.631%	$33.9841	$33.98	$34.00	$34.00
Purchase #4	$136.92	12.557%	$154.113	$154.11	$154.10	$154.10
Purchase #5	$226.26	4.510%	$236.4643	$236.46	$236.45	$236.50
Purchase #6	$75.32	4.169%	$78.4601	$78.46	$78.45	$78.50
Purchase #7	$181.38	5.633%	$191.5971	$191.60	$191.60	$191.60
7 purchase totals =	$899.41		$968.8276	$968.82	$968.80	$969.00