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	$41.29	3.787%	$42.8537	$42.85	$42.85	$42.90
Purchase #2	$244.35	7.856%	$263.5461	$263.55	$263.55	$263.50
Purchase #3	$28.30	4.377%	$29.5387	$29.54	$29.55	$29.50
Purchase #4	$127.54	10.643%	$141.1141	$141.11	$141.10	$141.10
Purchase #5	$13.54	6.250%	$14.3863	$14.39	$14.40	$14.40
Purchase #6	$245.87	13.667%	$279.4731	$279.47	$279.45	$279.50
Purchase #7	$166.95	10.487%	$184.458	$184.46	$184.45	$184.50
7 purchase totals =	$867.84		$955.3700	$955.37	$955.35	$955.40