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	$44.36	8.341%	$48.0601	$48.06	$48.05	$48.10
Purchase #2	$238.27	10.591%	$263.5052	$263.51	$263.50	$263.50
Purchase #3	$158.46	4.447%	$165.5067	$165.51	$165.50	$165.50
Purchase #4	$28.67	9.105%	$31.2804	$31.28	$31.30	$31.30
Purchase #5	$242.37	8.478%	$262.9181	$262.92	$262.90	$262.90
Purchase #6	$9.86	6.136%	$10.465	$10.47	$10.45	$10.50
Purchase #7	$96.91	13.202%	$109.7041	$109.70	$109.70	$109.70
7 purchase totals =	$818.90		$891.4396	$891.45	$891.40	$891.50