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	$145.63	13.751%	$165.6556	$165.66	$165.65	$165.70
Purchase #2	$191.59	11.824%	$214.2436	$214.24	$214.25	$214.20
Purchase #3	$87.72	10.566%	$96.9885	$96.99	$97.00	$97.00
Purchase #4	$139.63	13.682%	$158.7342	$158.73	$158.75	$158.70
Purchase #5	$131.48	11.288%	$146.3215	$146.32	$146.30	$146.30
Purchase #6	$119.50	3.660%	$123.8737	$123.87	$123.85	$123.90
Purchase #7	$114.35	7.692%	$123.1458	$123.15	$123.15	$123.10
7 purchase totals =	$929.90		$1,028.9629	$1,028.96	$1,028.95	$1,028.90