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	$41.27	6.498%	$43.9517	$43.95	$43.95	$44.00
Purchase #2	$62.67	5.164%	$65.9063	$65.91	$65.90	$65.90
Purchase #3	$11.74	13.212%	$13.2911	$13.29	$13.30	$13.30
Purchase #4	$168.42	9.276%	$184.0426	$184.04	$184.05	$184.00
Purchase #5	$134.52	7.305%	$144.3467	$144.35	$144.35	$144.30
Purchase #6	$86.94	3.862%	$90.2976	$90.30	$90.30	$90.30
Purchase #7	$100.37	8.154%	$108.5542	$108.55	$108.55	$108.60
7 purchase totals =	$605.93		$650.3902	$650.39	$650.40	$650.40