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	$106.82	11.146%	$118.7262	$118.73	$118.75	$118.70
Purchase #2	$230.98	4.501%	$241.3764	$241.38	$241.40	$241.40
Purchase #3	$221.47	11.613%	$247.1893	$247.19	$247.20	$247.20
Purchase #4	$52.39	9.709%	$57.4765	$57.48	$57.50	$57.50
Purchase #5	$10.98	5.437%	$11.577	$11.58	$11.60	$11.60
Purchase #6	$250.54	12.395%	$281.5944	$281.59	$281.60	$281.60
Purchase #7	$177.45	5.650%	$187.4759	$187.48	$187.50	$187.50
7 purchase totals =	$1,050.63		$1,145.4157	$1,145.43	$1,145.55	$1,145.50