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	$136.58	10.432%	$150.828	$150.83	$150.85	$150.80
Purchase #2	$142.55	12.837%	$160.8491	$160.85	$160.85	$160.80
Purchase #3	$53.52	11.728%	$59.7968	$59.80	$59.80	$59.80
Purchase #4	$239.65	3.234%	$247.4003	$247.40	$247.40	$247.40
Purchase #5	$30.86	4.330%	$32.1962	$32.20	$32.20	$32.20
Purchase #6	$12.98	10.801%	$14.382	$14.38	$14.40	$14.40
Purchase #7	$48.98	11.244%	$54.4873	$54.49	$54.50	$54.50
7 purchase totals =	$665.12		$719.9397	$719.95	$720.00	$719.90