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	$22.86	9.133%	$24.9478	$24.95	$24.95	$24.90
Purchase #2	$49.31	9.192%	$53.8426	$53.84	$53.85	$53.80
Purchase #3	$112.39	13.197%	$127.2221	$127.22	$127.20	$127.20
Purchase #4	$17.37	3.749%	$18.0212	$18.02	$18.00	$18.00
Purchase #5	$126.27	12.165%	$141.6307	$141.63	$141.65	$141.60
Purchase #6	$34.27	7.761%	$36.9297	$36.93	$36.95	$36.90
Purchase #7	$53.72	3.301%	$55.4933	$55.49	$55.50	$55.50
7 purchase totals =	$416.19		$458.0874	$458.08	$458.10	$457.90