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	$144.88	12.579%	$163.1045	$163.10	$163.10	$163.10
Purchase #2	$131.61	10.504%	$145.4343	$145.43	$145.45	$145.40
Purchase #3	$201.28	5.477%	$212.3041	$212.30	$212.30	$212.30
Purchase #4	$95.75	13.852%	$109.0133	$109.01	$109.00	$109.00
Purchase #5	$174.25	9.599%	$190.9763	$190.98	$191.00	$191.00
Purchase #6	$86.28	5.144%	$90.7182	$90.72	$90.70	$90.70
Purchase #7	$109.46	12.857%	$123.5333	$123.53	$123.55	$123.50
7 purchase totals =	$943.51		$1,035.0840	$1,035.07	$1,035.10	$1,035.00