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	$61.83	4.236%	$64.4491	$64.45	$64.45	$64.40
Purchase #2	$182.50	12.748%	$205.7651	$205.77	$205.75	$205.80
Purchase #3	$85.42	7.233%	$91.5984	$91.60	$91.60	$91.60
Purchase #4	$236.30	8.156%	$255.5726	$255.57	$255.55	$255.60
Purchase #5	$38.48	9.298%	$42.0579	$42.06	$42.05	$42.10
Purchase #6	$37.79	11.657%	$42.1952	$42.20	$42.20	$42.20
Purchase #7	$10.47	10.531%	$11.5726	$11.57	$11.55	$11.60
7 purchase totals =	$652.79		$713.2109	$713.22	$713.15	$713.30