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	$213.74	12.650%	$240.7781	$240.78	$240.80	$240.80
Purchase #2	$96.28	4.818%	$100.9188	$100.92	$100.90	$100.90
Purchase #3	$132.36	11.541%	$147.6357	$147.64	$147.65	$147.60
Purchase #4	$241.95	7.423%	$259.9099	$259.91	$259.90	$259.90
Purchase #5	$91.73	3.649%	$95.0772	$95.08	$95.10	$95.10
Purchase #6	$162.68	12.657%	$183.2704	$183.27	$183.25	$183.30
Purchase #7	$117.60	11.328%	$130.9217	$130.92	$130.90	$130.90
7 purchase totals =	$1,056.34		$1,158.5118	$1,158.52	$1,158.50	$1,158.50