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	$232.75	11.450%	$259.3999	$259.40	$259.40	$259.40
Purchase #2	$31.76	6.703%	$33.8889	$33.89	$33.90	$33.90
Purchase #3	$45.74	9.153%	$49.9266	$49.93	$49.95	$49.90
Purchase #4	$150.52	10.171%	$165.8294	$165.83	$165.85	$165.80
Purchase #5	$235.60	5.331%	$248.1598	$248.16	$248.15	$248.20
Purchase #6	$123.80	3.667%	$128.3397	$128.34	$128.35	$128.30
Purchase #7	$126.47	4.383%	$132.0132	$132.01	$132.00	$132.00
7 purchase totals =	$946.64		$1,017.5575	$1,017.56	$1,017.60	$1,017.50