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	$153.40	4.580%	$160.4257	$160.43	$160.45	$160.40
Purchase #2	$117.61	8.289%	$127.3587	$127.36	$127.35	$127.40
Purchase #3	$42.48	6.617%	$45.2909	$45.29	$45.30	$45.30
Purchase #4	$56.89	5.630%	$60.0929	$60.09	$60.10	$60.10
Purchase #5	$48.68	8.158%	$52.6513	$52.65	$52.65	$52.70
Purchase #6	$96.83	4.190%	$100.8872	$100.89	$100.90	$100.90
Purchase #7	$237.68	6.608%	$253.3859	$253.39	$253.40	$253.40
7 purchase totals =	$753.57		$800.0926	$800.10	$800.15	$800.20