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	$51.52	13.368%	$58.4072	$58.41	$58.40	$58.40
Purchase #2	$39.53	11.513%	$44.0811	$44.08	$44.10	$44.10
Purchase #3	$41.96	7.639%	$45.1653	$45.17	$45.15	$45.20
Purchase #4	$13.51	4.724%	$14.1482	$14.15	$14.15	$14.10
Purchase #5	$141.85	13.751%	$161.3558	$161.36	$161.35	$161.40
Purchase #6	$83.68	6.621%	$89.2205	$89.22	$89.20	$89.20
Purchase #7	$71.29	7.307%	$76.4992	$76.50	$76.50	$76.50
7 purchase totals =	$443.34		$488.8773	$488.89	$488.85	$488.90