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	$110.41	9.651%	$121.0657	$121.07	$121.05	$121.10
Purchase #2	$217.59	5.540%	$229.6445	$229.64	$229.65	$229.60
Purchase #3	$53.32	11.665%	$59.5398	$59.54	$59.55	$59.50
Purchase #4	$125.88	13.659%	$143.0739	$143.07	$143.05	$143.10
Purchase #5	$248.58	3.117%	$256.3282	$256.33	$256.35	$256.30
Purchase #6	$158.63	7.684%	$170.8191	$170.82	$170.80	$170.80
Purchase #7	$151.86	13.713%	$172.6846	$172.68	$172.70	$172.70
7 purchase totals =	$1,066.27		$1,153.1558	$1,153.15	$1,153.15	$1,153.10