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	$67.50	5.591%	$71.2739	$71.27	$71.25	$71.30
Purchase #2	$80.53	6.784%	$85.9932	$85.99	$86.00	$86.00
Purchase #3	$168.79	4.443%	$176.2893	$176.29	$176.30	$176.30
Purchase #4	$93.80	13.420%	$106.388	$106.39	$106.40	$106.40
Purchase #5	$191.48	7.104%	$205.0827	$205.08	$205.10	$205.10
Purchase #6	$232.98	9.713%	$255.6093	$255.61	$255.60	$255.60
Purchase #7	$143.58	7.698%	$154.6328	$154.63	$154.65	$154.60
7 purchase totals =	$978.66		$1,055.2692	$1,055.26	$1,055.30	$1,055.30