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	$61.54	9.461%	$67.3623	$67.36	$67.35	$67.40
Purchase #2	$242.67	12.422%	$272.8145	$272.81	$272.80	$272.80
Purchase #3	$186.66	4.697%	$195.4274	$195.43	$195.45	$195.40
Purchase #4	$222.32	8.790%	$241.8619	$241.86	$241.85	$241.90
Purchase #5	$153.89	13.628%	$174.8621	$174.86	$174.85	$174.90
Purchase #6	$220.35	8.118%	$238.238	$238.24	$238.25	$238.20
Purchase #7	$189.70	11.245%	$211.0318	$211.03	$211.05	$211.00
7 purchase totals =	$1,277.13		$1,401.5980	$1,401.59	$1,401.60	$1,401.60