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	$75.93	8.223%	$82.1737	$82.17	$82.15	$82.20
Purchase #2	$239.74	12.398%	$269.463	$269.46	$269.45	$269.50
Purchase #3	$118.55	4.823%	$124.2677	$124.27	$124.25	$124.30
Purchase #4	$110.85	11.419%	$123.508	$123.51	$123.50	$123.50
Purchase #5	$145.83	5.851%	$154.3625	$154.36	$154.35	$154.40
Purchase #6	$167.83	4.622%	$175.5871	$175.59	$175.60	$175.60
Purchase #7	$147.35	13.177%	$166.7663	$166.77	$166.75	$166.80
7 purchase totals =	$1,006.08		$1,096.1283	$1,096.13	$1,096.05	$1,096.30