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	$66.65	8.168%	$72.094	$72.09	$72.10	$72.10
Purchase #2	$167.86	10.647%	$185.7321	$185.73	$185.75	$185.70
Purchase #3	$54.29	12.836%	$61.2587	$61.26	$61.25	$61.30
Purchase #4	$176.29	5.865%	$186.6294	$186.63	$186.65	$186.60
Purchase #5	$194.80	13.858%	$221.7954	$221.80	$221.80	$221.80
Purchase #6	$102.46	10.853%	$113.58	$113.58	$113.60	$113.60
Purchase #7	$247.29	3.858%	$256.8304	$256.83	$256.85	$256.80
7 purchase totals =	$1,009.64		$1,097.9200	$1,097.92	$1,098.00	$1,097.90