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	$196.90	6.700%	$210.0923	$210.09	$210.10	$210.10
Purchase #2	$18.34	8.121%	$19.8294	$19.83	$19.85	$19.80
Purchase #3	$40.39	6.826%	$43.147	$43.15	$43.15	$43.10
Purchase #4	$78.71	5.718%	$83.2106	$83.21	$83.20	$83.20
Purchase #5	$132.55	5.133%	$139.3538	$139.35	$139.35	$139.40
Purchase #6	$167.45	11.827%	$187.2543	$187.25	$187.25	$187.30
Purchase #7	$51.71	9.540%	$56.6431	$56.64	$56.65	$56.60
7 purchase totals =	$686.05		$739.5305	$739.52	$739.55	$739.50