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	$118.30	8.209%	$128.0112	$128.01	$128.00	$128.00
Purchase #2	$104.66	6.187%	$111.1353	$111.14	$111.15	$111.10
Purchase #3	$163.63	12.803%	$184.5795	$184.58	$184.60	$184.60
Purchase #4	$225.50	8.669%	$245.0486	$245.05	$245.05	$245.00
Purchase #5	$36.71	10.659%	$40.6229	$40.62	$40.60	$40.60
Purchase #6	$188.63	4.394%	$196.9184	$196.92	$196.90	$196.90
Purchase #7	$202.59	12.773%	$228.4668	$228.47	$228.45	$228.50
7 purchase totals =	$1,040.02		$1,134.7827	$1,134.79	$1,134.75	$1,134.70