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	$79.82	3.235%	$82.4022	$82.40	$82.40	$82.40
Purchase #2	$131.25	4.783%	$137.5277	$137.53	$137.55	$137.50
Purchase #3	$162.90	5.612%	$172.0419	$172.04	$172.05	$172.00
Purchase #4	$43.70	13.593%	$49.6401	$49.64	$49.65	$49.60
Purchase #5	$222.80	7.338%	$239.1491	$239.15	$239.15	$239.10
Purchase #6	$181.49	13.238%	$205.5156	$205.52	$205.50	$205.50
Purchase #7	$117.53	9.146%	$128.2793	$128.28	$128.30	$128.30
7 purchase totals =	$939.49		$1,014.5559	$1,014.56	$1,014.60	$1,014.40