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	$119.68	9.821%	$131.4338	$131.43	$131.45	$131.40
Purchase #2	$51.41	5.505%	$54.2401	$54.24	$54.25	$54.20
Purchase #3	$83.75	6.460%	$89.1603	$89.16	$89.15	$89.20
Purchase #4	$213.86	11.212%	$237.838	$237.84	$237.85	$237.80
Purchase #5	$132.87	5.608%	$140.3213	$140.32	$140.30	$140.30
Purchase #6	$41.90	9.824%	$46.0163	$46.02	$46.00	$46.00
Purchase #7	$65.54	6.168%	$69.5825	$69.58	$69.60	$69.60
7 purchase totals =	$709.01		$768.5923	$768.59	$768.60	$768.50