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	$164.60	4.739%	$172.4004	$172.40	$172.40	$172.40
Purchase #2	$201.59	9.717%	$221.1785	$221.18	$221.20	$221.20
Purchase #3	$141.76	10.374%	$156.4662	$156.47	$156.45	$156.50
Purchase #4	$245.76	3.434%	$254.1994	$254.20	$254.20	$254.20
Purchase #5	$102.94	8.488%	$111.6775	$111.68	$111.70	$111.70
Purchase #6	$138.60	10.329%	$152.916	$152.92	$152.90	$152.90
Purchase #7	$89.99	9.781%	$98.7919	$98.79	$98.80	$98.80
7 purchase totals =	$1,085.24		$1,167.6299	$1,167.64	$1,167.65	$1,167.70