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	$240.42	8.446%	$260.7259	$260.73	$260.75	$260.70
Purchase #2	$104.73	6.740%	$111.7888	$111.79	$111.80	$111.80
Purchase #3	$144.86	5.784%	$153.2387	$153.24	$153.25	$153.20
Purchase #4	$95.43	10.782%	$105.7193	$105.72	$105.70	$105.70
Purchase #5	$94.28	13.154%	$106.6816	$106.68	$106.70	$106.70
Purchase #6	$50.78	3.821%	$52.7203	$52.72	$52.70	$52.70
Purchase #7	$31.45	9.478%	$34.4308	$34.43	$34.45	$34.40
7 purchase totals =	$761.95		$825.3054	$825.31	$825.35	$825.20