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	$225.67	8.206%	$244.1885	$244.19	$244.20	$244.20
Purchase #2	$153.71	5.603%	$162.3224	$162.32	$162.30	$162.30
Purchase #3	$95.68	9.323%	$104.6002	$104.60	$104.60	$104.60
Purchase #4	$17.89	5.752%	$18.919	$18.92	$18.90	$18.90
Purchase #5	$78.28	5.442%	$82.54	$82.54	$82.55	$82.50
Purchase #6	$171.53	9.341%	$187.5526	$187.55	$187.55	$187.60
Purchase #7	$49.43	6.342%	$52.5649	$52.56	$52.55	$52.60
7 purchase totals =	$792.19		$852.6876	$852.68	$852.65	$852.70