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	$13.46	5.148%	$14.1529	$14.15	$14.15	$14.20
Purchase #2	$41.89	9.149%	$45.7225	$45.72	$45.70	$45.70
Purchase #3	$125.86	9.653%	$138.0093	$138.01	$138.00	$138.00
Purchase #4	$79.39	12.273%	$89.1335	$89.13	$89.15	$89.10
Purchase #5	$65.72	8.219%	$71.1215	$71.12	$71.10	$71.10
Purchase #6	$24.37	11.636%	$27.2057	$27.21	$27.20	$27.20
Purchase #7	$196.70	5.495%	$207.5087	$207.51	$207.50	$207.50
7 purchase totals =	$547.39		$592.8541	$592.85	$592.80	$592.80