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	$208.81	9.169%	$227.9558	$227.96	$227.95	$228.00
Purchase #2	$71.53	13.691%	$81.3232	$81.32	$81.30	$81.30
Purchase #3	$180.54	6.551%	$192.3672	$192.37	$192.35	$192.40
Purchase #4	$29.78	4.224%	$31.0379	$31.04	$31.05	$31.00
Purchase #5	$35.64	13.817%	$40.5644	$40.56	$40.55	$40.60
Purchase #6	$54.81	11.718%	$61.2326	$61.23	$61.25	$61.20
Purchase #7	$58.51	3.200%	$60.3823	$60.38	$60.40	$60.40
7 purchase totals =	$639.62		$694.8634	$694.86	$694.85	$694.90