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	$194.86	13.647%	$221.4525	$221.45	$221.45	$221.50
Purchase #2	$60.45	5.549%	$63.8044	$63.80	$63.80	$63.80
Purchase #3	$135.47	4.486%	$141.5472	$141.55	$141.55	$141.50
Purchase #4	$168.44	4.162%	$175.4505	$175.45	$175.45	$175.50
Purchase #5	$24.71	11.358%	$27.5166	$27.52	$27.50	$27.50
Purchase #6	$73.58	11.546%	$82.0755	$82.08	$82.10	$82.10
Purchase #7	$38.51	5.170%	$40.501	$40.50	$40.50	$40.50
7 purchase totals =	$696.02		$752.3477	$752.35	$752.35	$752.40