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	$63.71	3.618%	$66.015	$66.02	$66.00	$66.00
Purchase #2	$42.78	13.534%	$48.5698	$48.57	$48.55	$48.60
Purchase #3	$24.36	3.364%	$25.1795	$25.18	$25.20	$25.20
Purchase #4	$32.31	12.509%	$36.3517	$36.35	$36.35	$36.40
Purchase #5	$244.41	4.579%	$255.6015	$255.60	$255.60	$255.60
Purchase #6	$143.62	11.793%	$160.5571	$160.56	$160.55	$160.60
Purchase #7	$64.44	11.773%	$72.0265	$72.03	$72.05	$72.00
7 purchase totals =	$615.63		$664.3011	$664.31	$664.30	$664.40