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	$64.93	10.320%	$71.6308	$71.63	$71.65	$71.60
Purchase #2	$34.95	6.150%	$37.0994	$37.10	$37.10	$37.10
Purchase #3	$237.53	7.600%	$255.5823	$255.58	$255.60	$255.60
Purchase #4	$74.74	5.208%	$78.6325	$78.63	$78.65	$78.60
Purchase #5	$153.56	10.823%	$170.1798	$170.18	$170.20	$170.20
Purchase #6	$208.50	3.439%	$215.6703	$215.67	$215.65	$215.70
Purchase #7	$190.98	12.546%	$214.9404	$214.94	$214.95	$214.90
7 purchase totals =	$965.19		$1,043.7355	$1,043.73	$1,043.80	$1,043.70