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	$47.61	10.455%	$52.5876	$52.59	$52.60	$52.60
Purchase #2	$143.61	13.103%	$162.4272	$162.43	$162.45	$162.40
Purchase #3	$111.87	11.569%	$124.8122	$124.81	$124.80	$124.80
Purchase #4	$234.71	10.433%	$259.1973	$259.20	$259.20	$259.20
Purchase #5	$188.88	7.734%	$203.488	$203.49	$203.50	$203.50
Purchase #6	$129.97	5.484%	$137.0976	$137.10	$137.10	$137.10
Purchase #7	$145.94	12.634%	$164.3781	$164.38	$164.40	$164.40
7 purchase totals =	$1,002.59		$1,103.9880	$1,104.00	$1,104.05	$1,104.00