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	$158.77	4.821%	$166.4243	$166.42	$166.40	$166.40
Purchase #2	$158.71	9.594%	$173.9366	$173.94	$173.95	$173.90
Purchase #3	$244.38	12.227%	$274.2603	$274.26	$274.25	$274.30
Purchase #4	$162.81	10.423%	$179.7797	$179.78	$179.80	$179.80
Purchase #5	$69.35	12.479%	$78.0042	$78.00	$78.00	$78.00
Purchase #6	$21.56	3.773%	$22.3735	$22.37	$22.35	$22.40
Purchase #7	$194.63	7.218%	$208.6784	$208.68	$208.70	$208.70
7 purchase totals =	$1,010.21		$1,103.4570	$1,103.45	$1,103.45	$1,103.50