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	$109.71	12.512%	$123.4369	$123.44	$123.45	$123.40
Purchase #2	$45.94	7.874%	$49.5573	$49.56	$49.55	$49.60
Purchase #3	$53.71	9.857%	$59.0042	$59.00	$59.00	$59.00
Purchase #4	$249.37	8.211%	$269.8458	$269.85	$269.85	$269.80
Purchase #5	$168.29	13.283%	$190.644	$190.64	$190.65	$190.60
Purchase #6	$192.72	6.711%	$205.6534	$205.65	$205.65	$205.70
Purchase #7	$164.78	9.290%	$180.0881	$180.09	$180.10	$180.10
7 purchase totals =	$984.52		$1,078.2297	$1,078.23	$1,078.25	$1,078.20