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	$174.89	4.476%	$182.7181	$182.72	$182.70	$182.70
Purchase #2	$164.70	11.467%	$183.5861	$183.59	$183.60	$183.60
Purchase #3	$88.75	12.814%	$100.1224	$100.12	$100.10	$100.10
Purchase #4	$95.28	9.631%	$104.4564	$104.46	$104.45	$104.50
Purchase #5	$239.36	7.176%	$256.5365	$256.54	$256.55	$256.50
Purchase #6	$114.34	5.576%	$120.7156	$120.72	$120.70	$120.70
Purchase #7	$219.66	5.174%	$231.0252	$231.03	$231.05	$231.00
7 purchase totals =	$1,096.98		$1,179.1603	$1,179.18	$1,179.15	$1,179.10