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	$44.26	12.526%	$49.804	$49.80	$49.80	$49.80
Purchase #2	$39.51	8.603%	$42.909	$42.91	$42.90	$42.90
Purchase #3	$230.85	10.802%	$255.7864	$255.79	$255.80	$255.80
Purchase #4	$128.55	10.780%	$142.4077	$142.41	$142.40	$142.40
Purchase #5	$184.41	10.402%	$203.5923	$203.59	$203.60	$203.60
Purchase #6	$106.41	5.144%	$111.8837	$111.88	$111.90	$111.90
Purchase #7	$204.40	12.540%	$230.0318	$230.03	$230.05	$230.00
7 purchase totals =	$938.39		$1,036.4149	$1,036.41	$1,036.45	$1,036.40