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	$40.70	7.680%	$43.8258	$43.83	$43.85	$43.80
Purchase #2	$211.31	10.852%	$234.2414	$234.24	$234.25	$234.20
Purchase #3	$40.72	6.215%	$43.2507	$43.25	$43.25	$43.30
Purchase #4	$11.97	12.773%	$13.4989	$13.50	$13.50	$13.50
Purchase #5	$156.30	13.183%	$176.905	$176.91	$176.90	$176.90
Purchase #6	$90.35	11.814%	$101.0239	$101.02	$101.00	$101.00
Purchase #7	$74.55	11.622%	$83.2142	$83.21	$83.20	$83.20
7 purchase totals =	$625.90		$695.9599	$695.96	$695.95	$695.90