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	$40.58	9.615%	$44.4818	$44.48	$44.50	$44.50
Purchase #2	$90.42	6.255%	$96.0758	$96.08	$96.10	$96.10
Purchase #3	$164.49	10.422%	$181.6331	$181.63	$181.65	$181.60
Purchase #4	$103.52	5.515%	$109.2291	$109.23	$109.25	$109.20
Purchase #5	$9.59	3.521%	$9.9277	$9.93	$9.95	$9.90
Purchase #6	$178.52	10.304%	$196.9147	$196.91	$196.90	$196.90
Purchase #7	$235.49	7.654%	$253.5144	$253.51	$253.50	$253.50
7 purchase totals =	$822.61		$891.7766	$891.77	$891.85	$891.70