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	$15.79	8.675%	$17.1598	$17.16	$17.15	$17.20
Purchase #2	$230.70	13.612%	$262.1029	$262.10	$262.10	$262.10
Purchase #3	$87.61	3.683%	$90.8367	$90.84	$90.85	$90.80
Purchase #4	$37.98	13.369%	$43.0575	$43.06	$43.05	$43.10
Purchase #5	$227.36	7.462%	$244.3256	$244.33	$244.35	$244.30
Purchase #6	$160.33	6.759%	$171.1667	$171.17	$171.15	$171.20
Purchase #7	$113.39	8.755%	$123.3173	$123.32	$123.30	$123.30
7 purchase totals =	$873.16		$951.9665	$951.98	$951.95	$952.00