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	$61.64	6.672%	$65.7526	$65.75	$65.75	$65.80
Purchase #2	$205.27	7.680%	$221.0347	$221.03	$221.05	$221.00
Purchase #3	$71.91	13.781%	$81.8199	$81.82	$81.80	$81.80
Purchase #4	$77.31	11.849%	$86.4705	$86.47	$86.45	$86.50
Purchase #5	$98.51	7.434%	$105.8332	$105.83	$105.85	$105.80
Purchase #6	$33.28	11.609%	$37.1435	$37.14	$37.15	$37.10
Purchase #7	$161.47	4.290%	$168.3971	$168.40	$168.40	$168.40
7 purchase totals =	$709.39		$766.4515	$766.44	$766.45	$766.40