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	$81.88	9.392%	$89.5702	$89.57	$89.55	$89.60
Purchase #2	$69.45	11.358%	$77.3381	$77.34	$77.35	$77.30
Purchase #3	$217.36	3.229%	$224.3786	$224.38	$224.40	$224.40
Purchase #4	$141.65	9.509%	$155.1195	$155.12	$155.10	$155.10
Purchase #5	$52.57	3.430%	$54.3732	$54.37	$54.35	$54.40
Purchase #6	$90.36	4.573%	$94.4922	$94.49	$94.50	$94.50
Purchase #7	$60.69	6.595%	$64.6925	$64.69	$64.70	$64.70
7 purchase totals =	$713.96		$759.9643	$759.96	$759.95	$760.00