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	$154.52	13.678%	$175.6552	$175.66	$175.65	$175.70
Purchase #2	$96.40	10.425%	$106.4497	$106.45	$106.45	$106.40
Purchase #3	$112.61	9.563%	$123.3789	$123.38	$123.40	$123.40
Purchase #4	$199.57	11.233%	$221.9877	$221.99	$222.00	$222.00
Purchase #5	$128.48	12.552%	$144.6068	$144.61	$144.60	$144.60
Purchase #6	$172.27	8.104%	$186.2308	$186.23	$186.25	$186.20
Purchase #7	$40.99	4.274%	$42.7419	$42.74	$42.75	$42.70
7 purchase totals =	$904.84		$1,001.0510	$1,001.06	$1,001.10	$1,001.00