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	$239.38	11.708%	$267.4066	$267.41	$267.40	$267.40
Purchase #2	$46.76	6.136%	$49.6292	$49.63	$49.65	$49.60
Purchase #3	$125.68	11.109%	$139.6418	$139.64	$139.65	$139.60
Purchase #4	$80.37	11.728%	$89.7958	$89.80	$89.80	$89.80
Purchase #5	$237.72	11.532%	$265.1339	$265.13	$265.15	$265.10
Purchase #6	$132.27	8.556%	$143.587	$143.59	$143.60	$143.60
Purchase #7	$42.53	11.193%	$47.2904	$47.29	$47.30	$47.30
7 purchase totals =	$904.71		$1,002.4847	$1,002.49	$1,002.55	$1,002.40