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	$244.86	6.555%	$260.9106	$260.91	$260.90	$260.90
Purchase #2	$101.33	9.722%	$111.1813	$111.18	$111.20	$111.20
Purchase #3	$173.77	12.799%	$196.0108	$196.01	$196.00	$196.00
Purchase #4	$48.77	10.444%	$53.8635	$53.86	$53.85	$53.90
Purchase #5	$205.41	9.791%	$225.5217	$225.52	$225.50	$225.50
Purchase #6	$103.64	4.809%	$108.624	$108.62	$108.60	$108.60
Purchase #7	$61.28	11.613%	$68.3964	$68.40	$68.40	$68.40
7 purchase totals =	$939.06		$1,024.5083	$1,024.50	$1,024.45	$1,024.50