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	$105.51	12.855%	$119.0733	$119.07	$119.05	$119.10
Purchase #2	$127.95	5.459%	$134.9348	$134.93	$134.95	$134.90
Purchase #3	$107.80	3.690%	$111.7778	$111.78	$111.80	$111.80
Purchase #4	$56.41	5.250%	$59.3715	$59.37	$59.35	$59.40
Purchase #5	$228.55	4.443%	$238.7045	$238.70	$238.70	$238.70
Purchase #6	$237.54	4.370%	$247.9205	$247.92	$247.90	$247.90
Purchase #7	$221.65	10.583%	$245.1072	$245.11	$245.10	$245.10
7 purchase totals =	$1,085.41		$1,156.8896	$1,156.88	$1,156.85	$1,156.90