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	$158.66	10.173%	$174.8005	$174.80	$174.80	$174.80
Purchase #2	$36.92	5.540%	$38.9654	$38.97	$38.95	$39.00
Purchase #3	$164.52	4.806%	$172.4268	$172.43	$172.45	$172.40
Purchase #4	$131.46	13.282%	$148.9205	$148.92	$148.90	$148.90
Purchase #5	$15.97	7.290%	$17.1342	$17.13	$17.15	$17.10
Purchase #6	$105.86	13.211%	$119.8452	$119.85	$119.85	$119.80
Purchase #7	$34.89	7.369%	$37.461	$37.46	$37.45	$37.50
7 purchase totals =	$648.28		$709.5536	$709.56	$709.55	$709.50