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	$250.60	13.784%	$285.1427	$285.14	$285.15	$285.10
Purchase #2	$98.40	5.110%	$103.4282	$103.43	$103.45	$103.40
Purchase #3	$123.38	3.816%	$128.0882	$128.09	$128.10	$128.10
Purchase #4	$103.45	3.800%	$107.3811	$107.38	$107.40	$107.40
Purchase #5	$11.58	12.725%	$13.0536	$13.05	$13.05	$13.10
Purchase #6	$205.70	6.602%	$219.2803	$219.28	$219.30	$219.30
Purchase #7	$168.91	6.501%	$179.8908	$179.89	$179.90	$179.90
7 purchase totals =	$962.02		$1,036.2649	$1,036.26	$1,036.35	$1,036.30