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	$124.56	13.598%	$141.4977	$141.50	$141.50	$141.50
Purchase #2	$186.66	12.464%	$209.9253	$209.93	$209.95	$209.90
Purchase #3	$187.65	4.631%	$196.3401	$196.34	$196.35	$196.30
Purchase #4	$41.45	5.163%	$43.5901	$43.59	$43.60	$43.60
Purchase #5	$117.53	12.698%	$132.454	$132.45	$132.45	$132.50
Purchase #6	$131.72	8.640%	$143.1006	$143.10	$143.10	$143.10
Purchase #7	$179.39	13.308%	$203.2632	$203.26	$203.25	$203.30
7 purchase totals =	$968.96		$1,070.1710	$1,070.17	$1,070.20	$1,070.20