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	$166.47	8.522%	$180.6566	$180.66	$180.65	$180.70
Purchase #2	$178.50	11.610%	$199.2239	$199.22	$199.20	$199.20
Purchase #3	$73.62	6.816%	$78.6379	$78.64	$78.65	$78.60
Purchase #4	$40.61	7.106%	$43.4957	$43.50	$43.50	$43.50
Purchase #5	$140.28	10.557%	$155.0894	$155.09	$155.10	$155.10
Purchase #6	$187.79	4.295%	$195.8556	$195.86	$195.85	$195.90
Purchase #7	$148.61	6.680%	$158.5371	$158.54	$158.55	$158.50
7 purchase totals =	$935.88		$1,011.4962	$1,011.51	$1,011.50	$1,011.50