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	$182.34	13.188%	$206.387	$206.39	$206.40	$206.40
Purchase #2	$115.69	10.258%	$127.5575	$127.56	$127.55	$127.60
Purchase #3	$111.51	13.211%	$126.2416	$126.24	$126.25	$126.20
Purchase #4	$51.42	11.295%	$57.2279	$57.23	$57.25	$57.20
Purchase #5	$162.56	5.730%	$171.8747	$171.87	$171.85	$171.90
Purchase #6	$159.31	9.221%	$174	$174.00	$174.00	$174.00
Purchase #7	$192.65	11.854%	$215.4867	$215.49	$215.50	$215.50
7 purchase totals =	$975.48		$1,078.7754	$1,078.78	$1,078.80	$1,078.80