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	$164.50	7.332%	$176.5611	$176.56	$176.55	$176.60
Purchase #2	$42.47	10.246%	$46.8215	$46.82	$46.80	$46.80
Purchase #3	$69.83	8.139%	$75.5135	$75.51	$75.50	$75.50
Purchase #4	$42.66	8.483%	$46.2788	$46.28	$46.30	$46.30
Purchase #5	$40.28	12.497%	$45.3138	$45.31	$45.30	$45.30
Purchase #6	$18.90	5.152%	$19.8737	$19.87	$19.85	$19.90
Purchase #7	$192.53	9.513%	$210.8454	$210.85	$210.85	$210.80
7 purchase totals =	$571.17		$621.2078	$621.20	$621.15	$621.20