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	$250.90	3.520%	$259.7317	$259.73	$259.75	$259.70
Purchase #2	$157.71	13.515%	$179.0245	$179.02	$179.00	$179.00
Purchase #3	$38.65	11.559%	$43.1176	$43.12	$43.10	$43.10
Purchase #4	$149.46	9.367%	$163.4599	$163.46	$163.45	$163.50
Purchase #5	$34.73	6.543%	$37.0024	$37.00	$37.00	$37.00
Purchase #6	$145.87	13.491%	$165.5493	$165.55	$165.55	$165.50
Purchase #7	$178.94	3.665%	$185.4982	$185.50	$185.50	$185.50
7 purchase totals =	$956.26		$1,033.3836	$1,033.38	$1,033.35	$1,033.30