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	$86.55	3.135%	$89.2633	$89.26	$89.25	$89.30
Purchase #2	$175.47	9.104%	$191.4448	$191.44	$191.45	$191.40
Purchase #3	$26.72	3.772%	$27.7279	$27.73	$27.75	$27.70
Purchase #4	$169.72	13.630%	$192.8528	$192.85	$192.85	$192.90
Purchase #5	$89.92	6.354%	$95.6335	$95.63	$95.65	$95.60
Purchase #6	$141.89	13.449%	$160.9728	$160.97	$160.95	$161.00
Purchase #7	$177.44	10.513%	$196.0943	$196.09	$196.10	$196.10
7 purchase totals =	$867.71		$953.9894	$953.97	$954.00	$954.00