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	$206.39	8.688%	$224.3212	$224.32	$224.30	$224.30
Purchase #2	$53.50	7.575%	$57.5526	$57.55	$57.55	$57.60
Purchase #3	$243.99	3.238%	$251.8904	$251.89	$251.90	$251.90
Purchase #4	$214.78	3.621%	$222.5572	$222.56	$222.55	$222.60
Purchase #5	$46.76	6.508%	$49.8031	$49.80	$49.80	$49.80
Purchase #6	$187.65	6.739%	$200.2957	$200.30	$200.30	$200.30
Purchase #7	$34.56	10.308%	$38.1224	$38.12	$38.10	$38.10
7 purchase totals =	$987.63		$1,044.5426	$1,044.54	$1,044.50	$1,044.60