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	$181.75	3.226%	$187.6133	$187.61	$187.60	$187.60
Purchase #2	$84.51	12.761%	$95.2943	$95.29	$95.30	$95.30
Purchase #3	$106.25	4.783%	$111.3319	$111.33	$111.35	$111.30
Purchase #4	$176.81	4.366%	$184.5295	$184.53	$184.55	$184.50
Purchase #5	$210.28	8.336%	$227.8089	$227.81	$227.80	$227.80
Purchase #6	$143.73	13.841%	$163.6237	$163.62	$163.60	$163.60
Purchase #7	$83.56	13.732%	$95.0345	$95.03	$95.05	$95.00
7 purchase totals =	$986.89		$1,065.2361	$1,065.22	$1,065.25	$1,065.10