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	$132.51	10.364%	$146.2433	$146.24	$146.25	$146.20
Purchase #2	$14.73	6.740%	$15.7228	$15.72	$15.70	$15.70
Purchase #3	$66.34	4.678%	$69.4434	$69.44	$69.45	$69.40
Purchase #4	$248.90	12.824%	$280.8189	$280.82	$280.80	$280.80
Purchase #5	$33.71	10.707%	$37.3193	$37.32	$37.30	$37.30
Purchase #6	$60.78	7.641%	$65.4242	$65.42	$65.40	$65.40
Purchase #7	$49.31	5.773%	$52.1567	$52.16	$52.15	$52.20
7 purchase totals =	$606.28		$667.1286	$667.12	$667.05	$667.00