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	$36.81	12.480%	$41.4039	$41.40	$41.40	$41.40
Purchase #2	$118.82	11.818%	$132.8621	$132.86	$132.85	$132.90
Purchase #3	$22.77	6.180%	$24.1772	$24.18	$24.20	$24.20
Purchase #4	$57.83	7.443%	$62.1343	$62.13	$62.15	$62.10
Purchase #5	$137.27	13.856%	$156.2901	$156.29	$156.30	$156.30
Purchase #6	$59.84	3.389%	$61.868	$61.87	$61.85	$61.90
Purchase #7	$100.26	11.200%	$111.4891	$111.49	$111.50	$111.50
7 purchase totals =	$533.60		$590.2247	$590.22	$590.25	$590.30