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	$21.96	11.241%	$24.4285	$24.43	$24.45	$24.40
Purchase #2	$237.56	8.455%	$257.6457	$257.65	$257.65	$257.60
Purchase #3	$159.69	4.758%	$167.2881	$167.29	$167.30	$167.30
Purchase #4	$140.87	5.254%	$148.2713	$148.27	$148.25	$148.30
Purchase #5	$80.95	10.455%	$89.4133	$89.41	$89.40	$89.40
Purchase #6	$191.65	7.416%	$205.8628	$205.86	$205.85	$205.90
Purchase #7	$190.81	6.557%	$203.3214	$203.32	$203.30	$203.30
7 purchase totals =	$1,023.49		$1,096.2311	$1,096.23	$1,096.20	$1,096.20