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	$134.39	4.222%	$140.0639	$140.06	$140.05	$140.10
Purchase #2	$164.25	11.763%	$183.5707	$183.57	$183.55	$183.60
Purchase #3	$146.77	3.307%	$151.6237	$151.62	$151.60	$151.60
Purchase #4	$78.73	13.772%	$89.5727	$89.57	$89.55	$89.60
Purchase #5	$133.80	5.458%	$141.1028	$141.10	$141.10	$141.10
Purchase #6	$128.89	5.421%	$135.8771	$135.88	$135.90	$135.90
Purchase #7	$165.82	4.679%	$173.5787	$173.58	$173.60	$173.60
7 purchase totals =	$952.65		$1,015.3896	$1,015.38	$1,015.35	$1,015.50