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	$135.27	6.226%	$143.6919	$143.69	$143.70	$143.70
Purchase #2	$71.32	9.575%	$78.1489	$78.15	$78.15	$78.10
Purchase #3	$67.85	6.457%	$72.2311	$72.23	$72.25	$72.20
Purchase #4	$249.84	8.208%	$270.3469	$270.35	$270.35	$270.30
Purchase #5	$41.54	5.621%	$43.875	$43.88	$43.90	$43.90
Purchase #6	$168.60	3.136%	$173.8873	$173.89	$173.90	$173.90
Purchase #7	$224.92	11.702%	$251.2401	$251.24	$251.25	$251.20
7 purchase totals =	$959.34		$1,033.4212	$1,033.43	$1,033.50	$1,033.30