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	$230.57	12.579%	$259.5734	$259.57	$259.55	$259.60
Purchase #2	$12.57	5.470%	$13.2576	$13.26	$13.25	$13.30
Purchase #3	$162.52	13.552%	$184.5447	$184.54	$184.55	$184.50
Purchase #4	$160.74	9.645%	$176.2434	$176.24	$176.25	$176.20
Purchase #5	$104.66	3.794%	$108.6308	$108.63	$108.65	$108.60
Purchase #6	$241.88	9.766%	$265.502	$265.50	$265.50	$265.50
Purchase #7	$38.56	11.255%	$42.8999	$42.90	$42.90	$42.90
7 purchase totals =	$951.50		$1,050.6518	$1,050.64	$1,050.65	$1,050.60