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	$116.41	6.537%	$124.0197	$124.02	$124.00	$124.00
Purchase #2	$150.27	9.189%	$164.0783	$164.08	$164.10	$164.10
Purchase #3	$125.82	4.588%	$131.5926	$131.59	$131.60	$131.60
Purchase #4	$48.74	10.834%	$54.0205	$54.02	$54.00	$54.00
Purchase #5	$111.82	6.500%	$119.0883	$119.09	$119.10	$119.10
Purchase #6	$237.43	4.281%	$247.5944	$247.59	$247.60	$247.60
Purchase #7	$124.59	5.599%	$131.5658	$131.57	$131.55	$131.60
7 purchase totals =	$915.08		$971.9596	$971.96	$971.95	$972.00