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	$105.93	5.269%	$111.5115	$111.51	$111.50	$111.50
Purchase #2	$12.68	6.113%	$13.4551	$13.46	$13.45	$13.50
Purchase #3	$152.90	9.595%	$167.5708	$167.57	$167.55	$167.60
Purchase #4	$190.25	7.843%	$205.1713	$205.17	$205.15	$205.20
Purchase #5	$150.72	11.457%	$167.988	$167.99	$168.00	$168.00
Purchase #6	$193.75	11.208%	$215.4655	$215.47	$215.45	$215.50
Purchase #7	$81.30	10.575%	$89.8975	$89.90	$89.90	$89.90
7 purchase totals =	$887.53		$971.0597	$971.07	$971.00	$971.20