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	$196.42	9.856%	$215.7792	$215.78	$215.80	$215.80
Purchase #2	$123.92	12.214%	$139.0556	$139.06	$139.05	$139.10
Purchase #3	$149.93	7.530%	$161.2197	$161.22	$161.20	$161.20
Purchase #4	$51.66	4.530%	$54.0002	$54.00	$54.00	$54.00
Purchase #5	$100.82	8.646%	$109.5369	$109.54	$109.55	$109.50
Purchase #6	$47.74	13.280%	$54.0799	$54.08	$54.10	$54.10
Purchase #7	$19.69	3.468%	$20.3728	$20.37	$20.35	$20.40
7 purchase totals =	$690.18		$754.0443	$754.05	$754.05	$754.10