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	$248.58	11.668%	$277.5843	$277.58	$277.60	$277.60
Purchase #2	$137.85	5.538%	$145.4841	$145.48	$145.50	$145.50
Purchase #3	$95.78	10.381%	$105.7229	$105.72	$105.70	$105.70
Purchase #4	$161.86	11.527%	$180.5176	$180.52	$180.50	$180.50
Purchase #5	$127.61	7.673%	$137.4015	$137.40	$137.40	$137.40
Purchase #6	$148.32	4.116%	$154.4249	$154.42	$154.40	$154.40
Purchase #7	$137.37	5.165%	$144.4652	$144.47	$144.45	$144.50
7 purchase totals =	$1,057.37		$1,145.6005	$1,145.59	$1,145.55	$1,145.60