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	$160.82	8.821%	$175.0059	$175.01	$175.00	$175.00
Purchase #2	$150.46	5.269%	$158.3877	$158.39	$158.40	$158.40
Purchase #3	$139.42	3.387%	$144.1422	$144.14	$144.15	$144.10
Purchase #4	$33.61	8.229%	$36.3758	$36.38	$36.40	$36.40
Purchase #5	$57.75	12.614%	$65.0346	$65.03	$65.05	$65.00
Purchase #6	$66.37	6.352%	$70.5858	$70.59	$70.60	$70.60
Purchase #7	$234.47	10.179%	$258.3367	$258.34	$258.35	$258.30
7 purchase totals =	$842.90		$907.8687	$907.88	$907.95	$907.80