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	$145.48	13.175%	$164.647	$164.65	$164.65	$164.60
Purchase #2	$142.97	5.341%	$150.606	$150.61	$150.60	$150.60
Purchase #3	$112.55	11.196%	$125.1511	$125.15	$125.15	$125.20
Purchase #4	$150.35	12.250%	$168.7679	$168.77	$168.75	$168.80
Purchase #5	$142.31	8.218%	$154.005	$154.01	$154.00	$154.00
Purchase #6	$241.89	12.269%	$271.5675	$271.57	$271.55	$271.60
Purchase #7	$188.92	11.226%	$210.1282	$210.13	$210.15	$210.10
7 purchase totals =	$1,124.47		$1,244.8727	$1,244.89	$1,244.85	$1,244.90