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	$142.78	7.409%	$153.3586	$153.36	$153.35	$153.40
Purchase #2	$215.59	10.653%	$238.5568	$238.56	$238.55	$238.60
Purchase #3	$62.32	4.418%	$65.0733	$65.07	$65.05	$65.10
Purchase #4	$19.61	11.255%	$21.8171	$21.82	$21.80	$21.80
Purchase #5	$153.38	7.799%	$165.3421	$165.34	$165.35	$165.30
Purchase #6	$24.85	13.247%	$28.1419	$28.14	$28.15	$28.10
Purchase #7	$41.69	11.696%	$46.5661	$46.57	$46.55	$46.60
7 purchase totals =	$660.22		$718.8559	$718.86	$718.80	$718.90