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	$215.60	12.324%	$242.1705	$242.17	$242.15	$242.20
Purchase #2	$161.72	9.164%	$176.54	$176.54	$176.55	$176.50
Purchase #3	$41.58	4.810%	$43.58	$43.58	$43.60	$43.60
Purchase #4	$31.42	7.164%	$33.6709	$33.67	$33.65	$33.70
Purchase #5	$215.55	5.661%	$227.7523	$227.75	$227.75	$227.80
Purchase #6	$194.37	3.335%	$200.8522	$200.85	$200.85	$200.90
Purchase #7	$236.37	4.464%	$246.9216	$246.92	$246.90	$246.90
7 purchase totals =	$1,096.61		$1,171.4875	$1,171.48	$1,171.45	$1,171.60