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	$60.50	7.130%	$64.8137	$64.81	$64.80	$64.80
Purchase #2	$64.66	11.405%	$72.0345	$72.03	$72.05	$72.00
Purchase #3	$92.32	8.428%	$100.1007	$100.10	$100.10	$100.10
Purchase #4	$196.39	6.797%	$209.7386	$209.74	$209.75	$209.70
Purchase #5	$153.95	5.622%	$162.6051	$162.61	$162.60	$162.60
Purchase #6	$73.48	11.626%	$82.0228	$82.02	$82.00	$82.00
Purchase #7	$102.48	4.675%	$107.2709	$107.27	$107.25	$107.30
7 purchase totals =	$743.78		$798.5863	$798.58	$798.55	$798.50