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	$164.75	12.564%	$185.4492	$185.45	$185.45	$185.40
Purchase #2	$21.38	4.787%	$22.4035	$22.40	$22.40	$22.40
Purchase #3	$41.50	10.551%	$45.8787	$45.88	$45.90	$45.90
Purchase #4	$104.37	3.201%	$107.7109	$107.71	$107.70	$107.70
Purchase #5	$43.50	12.255%	$48.8309	$48.83	$48.85	$48.80
Purchase #6	$82.75	3.715%	$85.8242	$85.82	$85.80	$85.80
Purchase #7	$234.70	8.685%	$255.0837	$255.08	$255.10	$255.10
7 purchase totals =	$692.95		$751.1811	$751.17	$751.20	$751.10