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	$97.81	10.545%	$108.1241	$108.12	$108.10	$108.10
Purchase #2	$164.80	5.180%	$173.3366	$173.34	$173.35	$173.30
Purchase #3	$147.31	9.218%	$160.889	$160.89	$160.90	$160.90
Purchase #4	$187.27	4.689%	$196.0511	$196.05	$196.05	$196.10
Purchase #5	$13.25	5.375%	$13.9622	$13.96	$13.95	$14.00
Purchase #6	$70.28	5.233%	$73.9578	$73.96	$73.95	$74.00
Purchase #7	$128.32	9.503%	$140.5142	$140.51	$140.50	$140.50
7 purchase totals =	$809.04		$866.8350	$866.83	$866.80	$866.90