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	$172.66	5.125%	$181.5088	$181.51	$181.50	$181.50
Purchase #2	$81.54	11.513%	$90.9277	$90.93	$90.95	$90.90
Purchase #3	$234.47	4.304%	$244.5616	$244.56	$244.55	$244.60
Purchase #4	$35.87	7.240%	$38.467	$38.47	$38.45	$38.50
Purchase #5	$67.32	10.685%	$74.5131	$74.51	$74.50	$74.50
Purchase #6	$123.51	6.622%	$131.6888	$131.69	$131.70	$131.70
Purchase #7	$227.37	5.691%	$240.3096	$240.31	$240.30	$240.30
7 purchase totals =	$942.74		$1,001.9766	$1,001.98	$1,001.95	$1,002.00