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	$62.60	8.393%	$67.854	$67.85	$67.85	$67.90
Purchase #2	$120.37	3.430%	$124.4987	$124.50	$124.50	$124.50
Purchase #3	$82.37	13.404%	$93.4109	$93.41	$93.40	$93.40
Purchase #4	$10.88	12.619%	$12.2529	$12.25	$12.25	$12.30
Purchase #5	$104.81	7.731%	$112.9129	$112.91	$112.90	$112.90
Purchase #6	$176.65	7.686%	$190.2273	$190.23	$190.25	$190.20
Purchase #7	$11.92	6.552%	$12.701	$12.70	$12.70	$12.70
7 purchase totals =	$569.60		$613.8577	$613.85	$613.85	$613.90