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	$150.99	9.126%	$164.7693	$164.77	$164.75	$164.80
Purchase #2	$161.84	6.375%	$172.1573	$172.16	$172.15	$172.20
Purchase #3	$105.42	7.136%	$112.9428	$112.94	$112.95	$112.90
Purchase #4	$105.97	7.590%	$114.0131	$114.01	$114.00	$114.00
Purchase #5	$228.46	12.177%	$256.2796	$256.28	$256.30	$256.30
Purchase #6	$159.88	13.217%	$181.0113	$181.01	$181.00	$181.00
Purchase #7	$136.46	4.582%	$142.7126	$142.71	$142.70	$142.70
7 purchase totals =	$1,049.02		$1,143.8860	$1,143.88	$1,143.85	$1,143.90