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	$100.66	4.404%	$105.0931	$105.09	$105.10	$105.10
Purchase #2	$107.42	3.808%	$111.5106	$111.51	$111.50	$111.50
Purchase #3	$34.82	8.853%	$37.9026	$37.90	$37.90	$37.90
Purchase #4	$47.68	6.717%	$50.8827	$50.88	$50.90	$50.90
Purchase #5	$168.57	4.605%	$176.3326	$176.33	$176.35	$176.30
Purchase #6	$212.35	10.267%	$234.152	$234.15	$234.15	$234.20
Purchase #7	$74.47	10.801%	$82.5135	$82.51	$82.50	$82.50
7 purchase totals =	$745.97		$798.3871	$798.37	$798.40	$798.40