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	$79.38	11.596%	$88.5849	$88.58	$88.60	$88.60
Purchase #2	$71.70	12.403%	$80.593	$80.59	$80.60	$80.60
Purchase #3	$238.92	8.310%	$258.7743	$258.77	$258.75	$258.80
Purchase #4	$188.77	13.852%	$214.9184	$214.92	$214.90	$214.90
Purchase #5	$247.83	3.276%	$255.9489	$255.95	$255.95	$255.90
Purchase #6	$78.93	6.266%	$83.8758	$83.88	$83.90	$83.90
Purchase #7	$135.70	7.138%	$145.3863	$145.39	$145.40	$145.40
7 purchase totals =	$1,041.23		$1,128.0816	$1,128.08	$1,128.10	$1,128.10