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	$153.26	12.493%	$172.4068	$172.41	$172.40	$172.40
Purchase #2	$64.63	12.833%	$72.924	$72.92	$72.90	$72.90
Purchase #3	$107.45	5.106%	$112.9364	$112.94	$112.95	$112.90
Purchase #4	$8.56	10.768%	$9.4817	$9.48	$9.50	$9.50
Purchase #5	$123.53	11.254%	$137.4321	$137.43	$137.45	$137.40
Purchase #6	$53.91	9.870%	$59.2309	$59.23	$59.25	$59.20
Purchase #7	$132.27	3.685%	$137.1441	$137.14	$137.15	$137.10
7 purchase totals =	$643.61		$701.5560	$701.55	$701.60	$701.40