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	$40.81	13.690%	$46.3969	$46.40	$46.40	$46.40
Purchase #2	$57.92	5.572%	$61.1473	$61.15	$61.15	$61.10
Purchase #3	$53.97	9.176%	$58.9223	$58.92	$58.90	$58.90
Purchase #4	$151.61	11.309%	$168.7556	$168.76	$168.75	$168.80
Purchase #5	$153.98	11.683%	$171.9695	$171.97	$171.95	$172.00
Purchase #6	$57.58	13.298%	$65.237	$65.24	$65.25	$65.20
Purchase #7	$76.83	9.155%	$83.8638	$83.86	$83.85	$83.90
7 purchase totals =	$592.70		$656.2924	$656.30	$656.25	$656.30