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	$105.94	5.162%	$111.4086	$111.41	$111.40	$111.40
Purchase #2	$182.31	11.243%	$202.8071	$202.81	$202.80	$202.80
Purchase #3	$192.45	5.755%	$203.5255	$203.53	$203.55	$203.50
Purchase #4	$120.37	6.632%	$128.3529	$128.35	$128.35	$128.40
Purchase #5	$180.70	10.849%	$200.3041	$200.30	$200.30	$200.30
Purchase #6	$180.59	5.444%	$190.4213	$190.42	$190.40	$190.40
Purchase #7	$110.38	3.832%	$114.6098	$114.61	$114.60	$114.60
7 purchase totals =	$1,072.74		$1,151.4293	$1,151.43	$1,151.40	$1,151.40