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	$246.47	6.673%	$262.9169	$262.92	$262.90	$262.90
Purchase #2	$160.76	3.842%	$166.9364	$166.94	$166.95	$166.90
Purchase #3	$148.87	13.256%	$168.6042	$168.60	$168.60	$168.60
Purchase #4	$82.43	10.185%	$90.8255	$90.83	$90.85	$90.80
Purchase #5	$39.92	11.293%	$44.4282	$44.43	$44.45	$44.40
Purchase #6	$113.60	8.591%	$123.3594	$123.36	$123.35	$123.40
Purchase #7	$216.74	3.485%	$224.2934	$224.29	$224.30	$224.30
7 purchase totals =	$1,008.79		$1,081.3640	$1,081.37	$1,081.40	$1,081.30