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	$224.52	6.384%	$238.8534	$238.85	$238.85	$238.90
Purchase #2	$84.87	8.167%	$91.8013	$91.80	$91.80	$91.80
Purchase #3	$50.62	10.158%	$55.762	$55.76	$55.75	$55.80
Purchase #4	$176.35	3.612%	$182.7198	$182.72	$182.70	$182.70
Purchase #5	$176.38	12.657%	$198.7044	$198.70	$198.70	$198.70
Purchase #6	$159.79	9.439%	$174.8726	$174.87	$174.85	$174.90
Purchase #7	$111.33	10.576%	$123.1043	$123.10	$123.10	$123.10
7 purchase totals =	$983.86		$1,065.8178	$1,065.80	$1,065.75	$1,065.90