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	$164.48	7.601%	$176.9821	$176.98	$177.00	$177.00
Purchase #2	$128.66	13.104%	$145.5196	$145.52	$145.50	$145.50
Purchase #3	$134.90	6.318%	$143.423	$143.42	$143.40	$143.40
Purchase #4	$188.54	4.229%	$196.5134	$196.51	$196.50	$196.50
Purchase #5	$59.95	12.582%	$67.4929	$67.49	$67.50	$67.50
Purchase #6	$129.45	7.262%	$138.8507	$138.85	$138.85	$138.90
Purchase #7	$15.81	3.672%	$16.3905	$16.39	$16.40	$16.40
7 purchase totals =	$821.79		$885.1722	$885.16	$885.15	$885.20