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	$72.94	8.175%	$78.9028	$78.90	$78.90	$78.90
Purchase #2	$77.91	8.792%	$84.7598	$84.76	$84.75	$84.80
Purchase #3	$53.97	7.528%	$58.0329	$58.03	$58.05	$58.00
Purchase #4	$72.46	10.761%	$80.2574	$80.26	$80.25	$80.30
Purchase #5	$137.69	9.506%	$150.7788	$150.78	$150.80	$150.80
Purchase #6	$94.25	10.157%	$103.823	$103.82	$103.80	$103.80
Purchase #7	$127.55	11.699%	$142.4721	$142.47	$142.45	$142.50
7 purchase totals =	$636.77		$699.0268	$699.02	$699.00	$699.10