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	$72.71	13.137%	$82.2619	$82.26	$82.25	$82.30
Purchase #2	$178.35	12.343%	$200.3637	$200.36	$200.35	$200.40
Purchase #3	$72.49	13.353%	$82.1696	$82.17	$82.15	$82.20
Purchase #4	$37.84	3.491%	$39.161	$39.16	$39.15	$39.20
Purchase #5	$231.80	12.649%	$261.1204	$261.12	$261.10	$261.10
Purchase #6	$169.88	6.723%	$181.301	$181.30	$181.30	$181.30
Purchase #7	$24.35	13.590%	$27.6592	$27.66	$27.65	$27.70
7 purchase totals =	$787.42		$874.0368	$874.03	$873.95	$874.20