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	$33.58	9.395%	$36.7348	$36.73	$36.75	$36.70
Purchase #2	$19.73	8.317%	$21.3709	$21.37	$21.35	$21.40
Purchase #3	$55.35	13.575%	$62.8638	$62.86	$62.85	$62.90
Purchase #4	$180.53	5.753%	$190.9159	$190.92	$190.90	$190.90
Purchase #5	$171.36	10.385%	$189.1557	$189.16	$189.15	$189.20
Purchase #6	$49.85	9.330%	$54.501	$54.50	$54.50	$54.50
Purchase #7	$70.83	8.479%	$76.8357	$76.84	$76.85	$76.80
7 purchase totals =	$581.23		$632.3778	$632.38	$632.35	$632.40