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	$151.34	11.509%	$168.7577	$168.76	$168.75	$168.80
Purchase #2	$98.84	6.707%	$105.4692	$105.47	$105.45	$105.50
Purchase #3	$194.91	8.234%	$210.9589	$210.96	$210.95	$211.00
Purchase #4	$112.96	3.446%	$116.8526	$116.85	$116.85	$116.90
Purchase #5	$10.50	3.834%	$10.9026	$10.90	$10.90	$10.90
Purchase #6	$121.72	3.561%	$126.0544	$126.05	$126.05	$126.10
Purchase #7	$29.37	9.328%	$32.1096	$32.11	$32.10	$32.10
7 purchase totals =	$719.64		$771.1050	$771.10	$771.05	$771.30