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	$101.93	7.572%	$109.6481	$109.65	$109.65	$109.60
Purchase #2	$128.88	10.546%	$142.4717	$142.47	$142.45	$142.50
Purchase #3	$113.53	13.544%	$128.9065	$128.91	$128.90	$128.90
Purchase #4	$183.70	9.719%	$201.5538	$201.55	$201.55	$201.60
Purchase #5	$123.44	11.427%	$137.5455	$137.55	$137.55	$137.50
Purchase #6	$168.25	10.433%	$185.8035	$185.80	$185.80	$185.80
Purchase #7	$136.83	5.123%	$143.8398	$143.84	$143.85	$143.80
7 purchase totals =	$956.56		$1,049.7689	$1,049.77	$1,049.75	$1,049.70