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	$29.54	5.435%	$31.1455	$31.15	$31.15	$31.10
Purchase #2	$73.98	6.677%	$78.9196	$78.92	$78.90	$78.90
Purchase #3	$44.51	8.517%	$48.3009	$48.30	$48.30	$48.30
Purchase #4	$231.89	5.345%	$244.2845	$244.28	$244.30	$244.30
Purchase #5	$56.49	5.258%	$59.4602	$59.46	$59.45	$59.50
Purchase #6	$104.51	11.118%	$116.1294	$116.13	$116.15	$116.10
Purchase #7	$160.72	10.873%	$178.1951	$178.20	$178.20	$178.20
7 purchase totals =	$701.64		$756.4352	$756.44	$756.45	$756.40