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	$174.60	13.389%	$197.9772	$197.98	$198.00	$198.00
Purchase #2	$117.69	8.184%	$127.3217	$127.32	$127.30	$127.30
Purchase #3	$17.68	12.704%	$19.9261	$19.93	$19.95	$19.90
Purchase #4	$19.74	8.451%	$21.4082	$21.41	$21.40	$21.40
Purchase #5	$52.92	12.604%	$59.59	$59.59	$59.60	$59.60
Purchase #6	$192.59	11.782%	$215.281	$215.28	$215.30	$215.30
Purchase #7	$107.30	12.786%	$121.0194	$121.02	$121.00	$121.00
7 purchase totals =	$682.52		$762.5236	$762.53	$762.55	$762.50