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	$114.74	10.752%	$127.0768	$127.08	$127.10	$127.10
Purchase #2	$168.34	9.397%	$184.1589	$184.16	$184.15	$184.20
Purchase #3	$178.69	8.439%	$193.7696	$193.77	$193.75	$193.80
Purchase #4	$116.57	9.751%	$127.9367	$127.94	$127.95	$127.90
Purchase #5	$105.47	3.102%	$108.7417	$108.74	$108.75	$108.70
Purchase #6	$140.74	8.442%	$152.6213	$152.62	$152.60	$152.60
Purchase #7	$84.82	5.128%	$89.1696	$89.17	$89.15	$89.20
7 purchase totals =	$909.37		$983.4746	$983.48	$983.45	$983.50