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	$79.89	3.483%	$82.6726	$82.67	$82.65	$82.70
Purchase #2	$166.90	12.624%	$187.9695	$187.97	$187.95	$188.00
Purchase #3	$166.43	8.436%	$180.47	$180.47	$180.45	$180.50
Purchase #4	$186.35	10.433%	$205.7919	$205.79	$205.80	$205.80
Purchase #5	$89.30	4.709%	$93.5051	$93.51	$93.50	$93.50
Purchase #6	$77.52	5.381%	$81.6914	$81.69	$81.70	$81.70
Purchase #7	$181.29	3.218%	$187.1239	$187.12	$187.10	$187.10
7 purchase totals =	$947.68		$1,019.2244	$1,019.22	$1,019.15	$1,019.30