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	$89.59	13.632%	$101.8029	$101.80	$101.80	$101.80
Purchase #2	$32.98	11.457%	$36.7585	$36.76	$36.75	$36.80
Purchase #3	$103.68	5.589%	$109.4747	$109.47	$109.45	$109.50
Purchase #4	$168.74	6.496%	$179.7014	$179.70	$179.70	$179.70
Purchase #5	$36.80	9.198%	$40.1849	$40.18	$40.20	$40.20
Purchase #6	$166.85	8.760%	$181.4661	$181.47	$181.45	$181.50
Purchase #7	$146.59	5.348%	$154.4296	$154.43	$154.45	$154.40
7 purchase totals =	$745.23		$803.8181	$803.81	$803.80	$803.90