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	$243.98	7.654%	$262.6542	$262.65	$262.65	$262.70
Purchase #2	$65.43	11.297%	$72.8216	$72.82	$72.80	$72.80
Purchase #3	$34.55	9.843%	$37.9508	$37.95	$37.95	$38.00
Purchase #4	$162.44	7.647%	$174.8618	$174.86	$174.85	$174.90
Purchase #5	$55.52	13.866%	$63.2184	$63.22	$63.20	$63.20
Purchase #6	$15.86	12.786%	$17.8879	$17.89	$17.90	$17.90
Purchase #7	$185.78	3.739%	$192.7263	$192.73	$192.75	$192.70
7 purchase totals =	$763.56		$822.1210	$822.12	$822.10	$822.20