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	$69.57	3.869%	$72.2617	$72.26	$72.25	$72.30
Purchase #2	$41.85	9.472%	$45.814	$45.81	$45.80	$45.80
Purchase #3	$41.95	4.730%	$43.9342	$43.93	$43.95	$43.90
Purchase #4	$140.28	13.581%	$159.3314	$159.33	$159.35	$159.30
Purchase #5	$228.49	12.276%	$256.5394	$256.54	$256.55	$256.50
Purchase #6	$214.85	3.729%	$222.8618	$222.86	$222.85	$222.90
Purchase #7	$5.76	11.162%	$6.4029	$6.40	$6.40	$6.40
7 purchase totals =	$742.75		$807.1454	$807.13	$807.15	$807.10