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	$162.54	9.463%	$177.9212	$177.92	$177.90	$177.90
Purchase #2	$195.35	13.242%	$221.2182	$221.22	$221.20	$221.20
Purchase #3	$144.57	11.232%	$160.8081	$160.81	$160.80	$160.80
Purchase #4	$111.83	4.470%	$116.8288	$116.83	$116.85	$116.80
Purchase #5	$56.64	7.734%	$61.0205	$61.02	$61.00	$61.00
Purchase #6	$76.40	3.163%	$78.8165	$78.82	$78.80	$78.80
Purchase #7	$247.94	10.652%	$274.3506	$274.35	$274.35	$274.40
7 purchase totals =	$995.27		$1,090.9639	$1,090.97	$1,090.90	$1,090.90