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	$119.72	7.384%	$128.5601	$128.56	$128.55	$128.60
Purchase #2	$47.97	9.611%	$52.5804	$52.58	$52.60	$52.60
Purchase #3	$19.37	12.716%	$21.8331	$21.83	$21.85	$21.80
Purchase #4	$164.41	12.413%	$184.8182	$184.82	$184.80	$184.80
Purchase #5	$76.88	11.602%	$85.7996	$85.80	$85.80	$85.80
Purchase #6	$241.49	10.477%	$266.7909	$266.79	$266.80	$266.80
Purchase #7	$218.91	4.843%	$229.5118	$229.51	$229.50	$229.50
7 purchase totals =	$888.75		$969.8941	$969.89	$969.90	$969.90