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	$199.55	11.595%	$222.6878	$222.69	$222.70	$222.70
Purchase #2	$115.41	10.665%	$127.7185	$127.72	$127.70	$127.70
Purchase #3	$102.80	11.134%	$114.2458	$114.25	$114.25	$114.20
Purchase #4	$203.88	4.712%	$213.4868	$213.49	$213.50	$213.50
Purchase #5	$147.58	13.475%	$167.4664	$167.47	$167.45	$167.50
Purchase #6	$44.67	8.314%	$48.3839	$48.38	$48.40	$48.40
Purchase #7	$44.92	9.800%	$49.3222	$49.32	$49.30	$49.30
7 purchase totals =	$858.81		$943.3114	$943.32	$943.30	$943.30