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	$148.27	9.612%	$162.5217	$162.52	$162.50	$162.50
Purchase #2	$148.83	3.783%	$154.4602	$154.46	$154.45	$154.50
Purchase #3	$34.62	7.667%	$37.2743	$37.27	$37.25	$37.30
Purchase #4	$172.65	9.832%	$189.6249	$189.62	$189.60	$189.60
Purchase #5	$172.98	4.221%	$180.2815	$180.28	$180.30	$180.30
Purchase #6	$176.45	9.696%	$193.5586	$193.56	$193.55	$193.60
Purchase #7	$124.57	6.523%	$132.6957	$132.70	$132.70	$132.70
7 purchase totals =	$978.37		$1,050.4169	$1,050.41	$1,050.35	$1,050.50