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	$92.52	5.290%	$97.4143	$97.41	$97.40	$97.40
Purchase #2	$73.25	7.210%	$78.5313	$78.53	$78.55	$78.50
Purchase #3	$180.85	10.109%	$199.1321	$199.13	$199.15	$199.10
Purchase #4	$152.30	12.680%	$171.6116	$171.61	$171.60	$171.60
Purchase #5	$29.76	7.503%	$31.9929	$31.99	$32.00	$32.00
Purchase #6	$20.37	7.738%	$21.9462	$21.95	$21.95	$21.90
Purchase #7	$113.81	3.522%	$117.8184	$117.82	$117.80	$117.80
7 purchase totals =	$662.86		$718.4468	$718.44	$718.45	$718.30