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	$145.60	3.491%	$150.6829	$150.68	$150.70	$150.70
Purchase #2	$90.27	4.503%	$94.3349	$94.33	$94.35	$94.30
Purchase #3	$98.94	4.411%	$103.3042	$103.30	$103.30	$103.30
Purchase #4	$76.94	4.349%	$80.2861	$80.29	$80.30	$80.30
Purchase #5	$239.53	6.465%	$255.0156	$255.02	$255.00	$255.00
Purchase #6	$226.33	4.376%	$236.2342	$236.23	$236.25	$236.20
Purchase #7	$160.75	11.102%	$178.5965	$178.60	$178.60	$178.60
7 purchase totals =	$1,038.36		$1,098.4544	$1,098.45	$1,098.50	$1,098.40