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	$172.60	11.157%	$191.857	$191.86	$191.85	$191.90
Purchase #2	$43.87	5.379%	$46.2298	$46.23	$46.25	$46.20
Purchase #3	$140.26	9.728%	$153.9045	$153.90	$153.90	$153.90
Purchase #4	$71.96	8.519%	$78.0903	$78.09	$78.10	$78.10
Purchase #5	$154.69	5.154%	$162.6627	$162.66	$162.65	$162.70
Purchase #6	$81.42	12.857%	$91.8882	$91.89	$91.90	$91.90
Purchase #7	$77.52	7.508%	$83.3402	$83.34	$83.35	$83.30
7 purchase totals =	$742.32		$807.9727	$807.97	$808.00	$808.00