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	$136.32	7.152%	$146.0696	$146.07	$146.05	$146.10
Purchase #2	$248.43	7.109%	$266.0909	$266.09	$266.10	$266.10
Purchase #3	$26.41	7.817%	$28.4745	$28.47	$28.45	$28.50
Purchase #4	$177.74	10.636%	$196.6444	$196.64	$196.65	$196.60
Purchase #5	$139.83	3.211%	$144.3199	$144.32	$144.30	$144.30
Purchase #6	$132.63	12.605%	$149.348	$149.35	$149.35	$149.30
Purchase #7	$126.99	3.716%	$131.7089	$131.71	$131.70	$131.70
7 purchase totals =	$988.35		$1,062.6562	$1,062.65	$1,062.60	$1,062.60