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	$54.96	7.453%	$59.0562	$59.06	$59.05	$59.10
Purchase #2	$5.82	11.134%	$6.468	$6.47	$6.45	$6.50
Purchase #3	$13.38	11.608%	$14.9332	$14.93	$14.95	$14.90
Purchase #4	$161.55	6.607%	$172.2236	$172.22	$172.20	$172.20
Purchase #5	$112.39	9.850%	$123.4604	$123.46	$123.45	$123.50
Purchase #6	$219.51	9.174%	$239.6478	$239.65	$239.65	$239.60
Purchase #7	$141.48	12.769%	$159.5456	$159.55	$159.55	$159.50
7 purchase totals =	$709.09		$775.3348	$775.34	$775.30	$775.30