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	$208.63	5.334%	$219.7583	$219.76	$219.75	$219.80
Purchase #2	$74.35	9.803%	$81.6385	$81.64	$81.65	$81.60
Purchase #3	$231.87	10.181%	$255.4767	$255.48	$255.50	$255.50
Purchase #4	$93.57	11.443%	$104.2772	$104.28	$104.30	$104.30
Purchase #5	$90.59	10.472%	$100.0766	$100.08	$100.10	$100.10
Purchase #6	$171.25	6.853%	$182.9858	$182.99	$183.00	$183.00
Purchase #7	$165.91	3.815%	$172.2395	$172.24	$172.25	$172.20
7 purchase totals =	$1,036.17		$1,116.4526	$1,116.47	$1,116.55	$1,116.50