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	$70.68	3.373%	$73.064	$73.06	$73.05	$73.10
Purchase #2	$57.60	3.724%	$59.745	$59.75	$59.75	$59.70
Purchase #3	$222.47	8.583%	$241.5646	$241.56	$241.55	$241.60
Purchase #4	$23.75	3.567%	$24.5972	$24.60	$24.60	$24.60
Purchase #5	$231.29	6.740%	$246.8789	$246.88	$246.90	$246.90
Purchase #6	$151.52	9.616%	$166.0902	$166.09	$166.10	$166.10
Purchase #7	$229.77	13.119%	$259.9135	$259.91	$259.90	$259.90
7 purchase totals =	$987.08		$1,071.8534	$1,071.85	$1,071.85	$1,071.90