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	$53.29	3.357%	$55.0789	$55.08	$55.10	$55.10
Purchase #2	$106.81	5.137%	$112.2968	$112.30	$112.30	$112.30
Purchase #3	$119.27	12.221%	$133.846	$133.85	$133.85	$133.80
Purchase #4	$37.55	12.319%	$42.1758	$42.18	$42.20	$42.20
Purchase #5	$181.59	3.862%	$188.603	$188.60	$188.60	$188.60
Purchase #6	$218.45	13.399%	$247.7201	$247.72	$247.70	$247.70
Purchase #7	$112.54	3.554%	$116.5397	$116.54	$116.55	$116.50
7 purchase totals =	$829.50		$896.2603	$896.27	$896.30	$896.20