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	$61.75	6.587%	$65.8175	$65.82	$65.80	$65.80
Purchase #2	$41.39	3.412%	$42.8022	$42.80	$42.80	$42.80
Purchase #3	$215.40	6.604%	$229.625	$229.63	$229.65	$229.60
Purchase #4	$102.94	9.218%	$112.429	$112.43	$112.45	$112.40
Purchase #5	$109.49	10.104%	$120.5529	$120.55	$120.55	$120.60
Purchase #6	$217.29	4.577%	$227.2354	$227.24	$227.25	$227.20
Purchase #7	$102.96	5.470%	$108.5919	$108.59	$108.60	$108.60
7 purchase totals =	$851.22		$907.0539	$907.06	$907.10	$907.00