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	$97.54	12.278%	$109.516	$109.52	$109.50	$109.50
Purchase #2	$19.94	4.175%	$20.7725	$20.77	$20.75	$20.80
Purchase #3	$51.71	13.570%	$58.727	$58.73	$58.75	$58.70
Purchase #4	$195.32	8.768%	$212.4457	$212.45	$212.45	$212.40
Purchase #5	$111.63	10.494%	$123.3445	$123.34	$123.35	$123.30
Purchase #6	$157.92	11.204%	$175.6134	$175.61	$175.60	$175.60
Purchase #7	$247.71	12.247%	$278.047	$278.05	$278.05	$278.00
7 purchase totals =	$881.77		$978.4661	$978.47	$978.45	$978.30