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	$206.45	4.326%	$215.381	$215.38	$215.40	$215.40
Purchase #2	$91.71	12.866%	$103.5094	$103.51	$103.50	$103.50
Purchase #3	$114.62	10.732%	$126.921	$126.92	$126.90	$126.90
Purchase #4	$48.91	10.606%	$54.0974	$54.10	$54.10	$54.10
Purchase #5	$154.72	8.696%	$168.1745	$168.17	$168.15	$168.20
Purchase #6	$84.41	5.613%	$89.1479	$89.15	$89.15	$89.10
Purchase #7	$143.96	4.289%	$150.1344	$150.13	$150.15	$150.10
7 purchase totals =	$844.78		$907.3656	$907.36	$907.35	$907.30