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	$157.68	12.165%	$176.8618	$176.86	$176.85	$176.90
Purchase #2	$219.77	5.272%	$231.3563	$231.36	$231.35	$231.40
Purchase #3	$198.73	9.841%	$218.287	$218.29	$218.30	$218.30
Purchase #4	$97.58	12.221%	$109.5053	$109.51	$109.50	$109.50
Purchase #5	$34.46	11.849%	$38.5432	$38.54	$38.55	$38.50
Purchase #6	$99.78	3.818%	$103.5896	$103.59	$103.60	$103.60
Purchase #7	$166.83	8.684%	$181.3175	$181.32	$181.30	$181.30
7 purchase totals =	$974.83		$1,059.4607	$1,059.47	$1,059.45	$1,059.50