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	$167.37	8.639%	$181.8291	$181.83	$181.85	$181.80
Purchase #2	$187.47	11.169%	$208.4085	$208.41	$208.40	$208.40
Purchase #3	$54.94	12.234%	$61.6614	$61.66	$61.65	$61.70
Purchase #4	$94.25	6.671%	$100.5374	$100.54	$100.55	$100.50
Purchase #5	$208.60	7.538%	$224.3243	$224.32	$224.30	$224.30
Purchase #6	$19.73	8.513%	$21.4096	$21.41	$21.40	$21.40
Purchase #7	$226.85	7.704%	$244.3265	$244.33	$244.35	$244.30
7 purchase totals =	$959.21		$1,042.4968	$1,042.50	$1,042.50	$1,042.40